Recipients of 'horse' in jars not happy (7)
I believe the answer is:
trojans
'recipients of horse' is the definition.
(received the Trojan Horse in Greek mythology)
'jars not happy' is the wordplay.
'happy' is an anagram indicator (happy can mean slightly drunk).
'jars'+'not'='jarsnot'
'jarsnot' is an anagram of 'TROJANS'.
'in' is the link.
(Other definitions for trojans that I've seen before include "Hard workers" , "People of Paris" , "noted for hard work" , "Citizens of ancient city in Asia Minor invaded by Wooden Horse" , "Hard-working types" .)