Rook caught in trap? Crow (4)
I believe the answer is:
brag
'crow' is the definition.
(I know that crow is a more specific form of brag)
'rook caught in trap?' is the wordplay.
'rook' becomes 'R' (chess abbreviation).
'caught in' indicates putting letters inside.
'trap?' becomes 'bag' (bag can mean to trap or secure).
'r' placed within 'bag' is 'BRAG'.
(Other definitions for brag that I've seen before include "Boast, exaggerate" , "Talk boastfully" , "'Show off, boast (4)'" , "Shoot a line" , "Card game - boast" .)