Following, cross, into trap (4)
I believe the answer is:
next
'following' is the definition.
('next' can be a synonym of 'following')
'cross into trap' is the wordplay.
'cross' becomes 'x' (**).
'into' is an insertion indicator.
'trap' becomes 'net' (net is a kind of trap).
'x' placed into 'net' is 'NEXT'.
(Other definitions for next that I've seen before include "The one following or adjacent" , "Coming nearest in order - come, please!" , "Coming nearest in time or sequence" , "Succeeding" , "Nearest following" .)