Leave behind band on a journey (7)
I believe the answer is:
abandon
'leave behind' is the definition.
(abandoning is a kind of leaving behind)
'band on a journey' is the wordplay.
'journey' indicates an anagram (I've seen 'journeying' mean this ( journeying suggests movement)).
'band'+'on'+'a'='bandona'
'bandona' is an anagram of 'ABANDON'.
(Other definitions for abandon that I've seen before include "Leave (a place) for ever" , "Leave behind - licentiousness" , "Permanently desert" , "Lack of inhibition; desert" , "Czech city" .)