Meet on the trip over (3,6)
I believe the answer is:
run across
'meet' is the definition.
(synonyms)
'the trip over' is the wordplay.
'the trip' becomes 'run' (run is a kind of trip).
'over' becomes 'across' (synonyms).
'run'+'across'='RUN ACROSS'
'on' acts as a link.
(Other definitions for run across that I've seen before include "what this answer doesn't do" , "Happen" , "Quickly reach the other side" , "Unexpectedly meet" , "Discover by chance" .)