Miss capturing rook — feeble! (5)
I believe the answer is:
frail
'feeble' is the definition.
('frail' can be similar in meaning to 'feeble')
'miss capturing rook' is the wordplay.
'miss' becomes 'fail' (failing is a kind of missing**).
'capturing' means one lot of letters goes inside another.
'rook' becomes 'r' (abbreviation in chess).
'fail' placed around 'r' is 'FRAIL'.
(Other definitions for frail that I've seen before include "Physically weak, delicate" , "Feeble - basket" , "rush" , "Weak and infirm" , "Easily destroyed" .)