Glimpsed some little devils (4)
I believe the answer is:
imps
'little devils' is the definition.
(I've seen this before)
'glimpsed some' is the wordplay.
'some' indicates the answer is hidden within the clue.
'IMPS' is hidden within 'glimpsed'.
(Other definitions for imps that I've seen before include "Small devils or mischievous children" , "Little rascals" , "Demons" , "Mischievous spirits" , "Naughty sprites" .)