Free trip, almost (3)
I believe the answer is:
rid
'free' is the definition.
('rid' can be a synonym of 'free')
'trip almost' is the wordplay.
'trip' becomes 'ride' (I've seen this before).
'almost' means to remove the last letter (most of the word but not all of it).
'ride' with its last letter removed is 'RID'.
(Other definitions for rid that I've seen before include "Free, disencumber" , "Clear, remove" , "Free, relieve" , "Free (someone of something unwanted)" , "Free (person of affliction)" .)