Attentive ambassador left after sorting out feud (7)
I believe the answer is:
heedful
'attentive' is the definition.
(heedful can mean listening or paying attention)
'ambassador left after sorting out feud' is the wordplay.
'ambassador' becomes 'HE' (His or Her Excellency).
'left' becomes 'l' (common abbreviation).
'after' says to put letters next to each other.
'sorting out' indicates anagramming the letters.
'feud' with letters rearranged gives 'edfu'.
'l' after 'edfu' is 'edful'.
'he'+'edful'='HEEDFUL'
(Other definitions for heedful that I've seen before include "Attentive, listening carefully" , "Prudent" , "Wary" , "Attentive - circumspect" , "Cautious" .)