Leave cab, seen drunk (7)
I believe the answer is:
absence
'leave' is the definition.
(thesaurus)
'cab seen drunk' is the wordplay.
'drunk' indicates anagramming the letters.
'cab'+'seen'='cabseen'
'cabseen' is an anagram of 'ABSENCE'.
(Other definitions for absence that I've seen before include "Cause of fonder heart?" , "Time off" , "Non-presence" , "Lack - it makes the heart grow fonder" , "what can be heart-warming?" .)