Party at end of short day is giving pleasure (12)
I believe the answer is:
satisfaction
'pleasure' is the definition.
(thesaurus)
'party at end of short day is' is the wordplay.
'party' becomes 'faction'.
'at end of' says to put letters next to each other.
'short day' becomes 'sat' (abbreviation for Saturday).
'sat'+'is'='satis'
'faction' after 'satis' is 'SATISFACTION'.
'giving' is the link.
(Other definitions for satisfaction that I've seen before include "I can't get no - (Rolling Stones)" , "Gratification" , "Pleasure" , "Contentment; reparation" , "Fulfilment; compensation" .)