Little Annie, somewhat thin (4)
I believe the answer is:
lean
'thin' is the definition.
('lean' is associated in meaning with 'thin')
'little annie somewhat' is the wordplay.
'somewhat' says the answer is hidden in the clue.
'LEAN' can be found hidden inside 'little annie'.
(Other definitions for lean that I've seen before include "Slight - incline" , "Unprofitable" , "without success" , "Current update (colloq.)" , "skinny" .)