Catches sweetheart in wood ... (5)
I believe the answer is:
copse
'wood' is the definition.
(a copse is a small wood)
'catches sweetheart' is the wordplay.
'catches' becomes 'cops' (cop can mean to apprehend).
'sweetheart' becomes 'e' (the heart/centre of 'sweet').
'cops'+'e'='COPSE'
'in' acts as a link.
(Other definitions for copse that I've seen before include "Small thicket" , "Clump of small trees for regular cropping" , "Cluster of trees" , "A little wood" , "Coppice" .)