Trail taking opposite directions back (7)
I believe the answer is:
sponsor
'back' is the definition.
(I've seen this before)
'trail taking opposite directions' is the wordplay.
'trail' becomes 'spoor' (spoor is a kind of trail).
'taking' indicates putting letters inside.
'opposite directions' becomes 'NS' (opposite compass points).
'spoor' enclosing 'ns' is 'SPONSOR'.
(Other definitions for sponsor that I've seen before include "One paying to support" , "advertising?" , "One financially supporting event" , "Promoter, godparent" , "One funding an event" .)