Catch some rising (4)
I believe the answer is:
trap
'catch' is the definition.
(I know that trap is a more specific form of the action catch)
'some rising' is the wordplay.
'some' becomes 'part' (only part of something).
'rising' shows that the letters should be reversed in order (in a down clue, letters go up).
'part' reversed gives 'TRAP'.
(Other definitions for trap that I've seen before include "Golfing hazard" , "that can let an actor down" , "that may be sprung?" , "Device to catch prey" , "Snare - mouth" .)