Fellow devours achievements (5)
I believe the answer is:
feats
'achievements' is the definition.
(feat is a kind of achievement)
'fellow devours' is the wordplay.
'fellow' becomes 'f' (abbreviation - of a society etc.).
'devours' becomes 'eats' (I've seen this in another clue).
'f'+'eats'='FEATS'
(Other definitions for feats that I've seen before include "Deeds, exploits" , "Stunts" .)