Nicene Creed by Flowerman

Four clues lack definitions. The answers to these clues must be modified before entry into the grid in accordance with 1ac, 50ac (6 words). Numbers in parentheses refer to grid entries. In the completed grid, two words (4) and (5) can be found which contradict what is expressed by 1ac, 50ac. These words must be highlighted.

See preamble
8  Tin backing protecting special device (5)
10  Wife out for run in beginning getting stitch (4)
12  Towers casting shadows at first on people in boat (4)
14  Dance in open scrubland not arranged (5)
15  Snake kicked out of the French cottage (4)
17  Gräfenberg Institute leaving volumes on anatomical structures (4)
18  Fish are feeling (4)
19  Asian country contracted to return soldiers' property (5)
21  A minor thrill when shitzu finally worked on a bone (5)
22  Nuclear material in reactor, naturally (3)
23  “Crafty” work with intelligence service halved on another's return (6)
24  Surprisingly good depth in unorthodox output from setter (3,2)
26  Mail disregarding royal's affair (5)
28  Get information from detailed record (3)
30  Orca's back in pursuit of male seal (5)
31  Distressed women breaking bread with German (5)
33  Old barrel in gutter (6)
35  Girl's South African relative dropping over (3)
37  Rib of vault in centre about to buckle (5)
41  Mammal using both hands to capture bird (5)
42  Brought back some jasmine trees from the east (4)
43  Souls from 47s out of cheese (4)
44  In Perth, champions recalled getting tight (4)
45  Crew wanting motorway largely clear for concluding part of work (5)
47  Ashamed about having no recipes for legume (4)
48  Worried but not hot when transported on this? (4)
49  Vessels in eastern 40 not hard to manoeuvre (5)
50  See preamble
1  One's left a long way up in tree (3)
2  Old soldier with heart failure, perhaps almost gave up before operation (8)
3  Government department climbing mountain (5)
4  Penny's filling up trusty old flower holder (5)
5  Croatian chap's heading down to get paper, maybe (5)
6  One excessively fond of 10ac turning up at party (6)
7  Abbey’s butler disregarding capital offence (5)
9  Nick's star is rising (5)
10  Dock weed at times choking channel (6)
11  Set up to advance shortly after noon (8)
13  Unionist interrupting sounds short on intelligence primarily (9)
16  Victorian coastal town turned up record (5)
17  Film fishing boats leaving the Heads (9)
20  Drink mostly hiding in bottom of dresser (8)
24  10ac doesn't have good level of proficiency (3)
25  Common alpine bee almost wiped out (8)
27  With these old characters about, client could become most angelic (5)
29  Master finding opening offloading old drugs (6)
32  International body in general putting out a ream of words (6)
34  Carol ringing Mark about defective item (5)
36  Set up outstanding medium for communications (5)
38  Determined to extinguish small fire in Glaswegian house (5)
39  Worse still, the local has abandoned boarding (5)
40  Give birth to son finally in shelter (5)
46  Categorise high school pants in Scottish sheds (3)

To enter this competition, send your entry as an image or in list format giving the highlighted parts to before 8th March 2017. The first correct entry drawn from the hat will receive a book from the Chambers range, which has been donated by Chambers.