Missing Letter by Urchin

In every clue (except one) there is an extra letter in the cryptic element. These extra letters, in normal clue order, give the names of six members of a group. Solvers should highlight in the grid a seventh member and a three word description of his role in the group.

Across

1 Rickets moves in cycles (6)
5 Pervert notes river (6)
10 Alternative boy's plants (7)
11 This he-cat unusually bears colour (7)
12 Formerly odd but possibly unmeditated? (6)
15 Horn gets learner in joke (6)
16 Marie is flying to trail sea birds (7)
17 Small beasts spoil feast (4)
18 Compose a letter or document, perhaps (4)
19 Boy (or young hooligan) clothed in fine attire (7)
20 Cool box galling to lose its head (4)
22 Make money with back to north (4)
25 Domenico composed in one voice (7)
27 Grass to clear up with big tent (6)
28 Energy in actors - they are ostracised (6)
31 Less intelligible power, otherwise describing most of Easter in Paris (7)
32 Signs of thrush in a heap spread round shed (7)
33 Fool governs a country for these people (6)
34 Optical devices observed in Saturnalias, erstwhile (6)

Down

2 River noble to tell a story (7)
3 Shirks round new weapons (6)
4 Eye over manuscript - enough said! (4)
5 Spread manure, turn in a short raincoat (4)
6 Sarsnet woven for bones (6)
7 Compiler pocketing pounds and shillings for a clerk in a betting shop (7)

8 Great circle cut up entering eccentric (6)
9 Hobart rioting with a republic (6)
13 Blowing powder over doctor gets you a pearl (3-4)
14 Character with white face, possibly a mole with a toddler (7)
15 Unmindful one, unfortunately, since I am (7)
20 Implant that's stitched too near (6)
21 King and queen get unnaturally shaded enclosures (7)
23 One more with a drop of Pernod could make you neuropath (7)
24 Egyptian statesman making sarnies (6)
25 Fly wife about after test (6)
26 Exhanges ace taken in by saps (6)
29 One out of terraces misses the mark (4)
30 Gauguin peut-être en chapeau large (4)

To enter this competition send the names of the six members plus the four highlighted words to derek@crosswordcentre.fsnet.co.uk before the 20 June. The first correct entry picked will win of Chambers collection of The Independent Book of Concise Crosswords, The Independent Book of Cryptic Crosswords and The Independent Book of Weekend Crosswords  which have been donated by the publishers.