In the morning I depart, leaving friend (5)
I believe the answer is:
amigo
'friend' is the definition.
(thesaurus)
'in the morning i depart' is the wordplay.
'in the morning' becomes 'am'.
'depart' becomes 'go' ('go' can be a synonym of 'depart').
'am'+'i'+'go'='AMIGO'
'leaving' acts as a link.
(Other definitions for amigo that I've seen before include "friend abroad" , "Quixote's friend" , "Mexican's mate" , "friend in Uruguay" , "China (in Spain's view)" .)