Trying to get behind? (5)
I believe the answer is:
after
I believe this clue is a double definition.
'trying to get' is the first definition.
(someone 'after' something is trying to get it)
'behind?' is the second definition.
(eg after or behind someone in a queue)
(Other definitions for after that I've seen before include "Subsequently" , "Following - behind" , "Searching for" , "In pursuit of, behind" , "Behind; in quest of" .)