Catch some climbing (4)
I believe the answer is:
trap
'catch' is the definition.
(trapping is a kind of catching)
'some climbing' is the wordplay.
'some' becomes 'part'.
'climbing' is a reversal indicator (in a down clue, letters climb up).
'part' written backwards gives 'TRAP'.
(Other definitions for trap that I've seen before include "It commonly has a role in speaking" , "Vehicle" , "Snare - mouth" , "Confine" , "Rock; carriage; gin" .)