Affair of love in a rum setting (5)
I believe the answer is:
amour
'affair' is the definition.
(amour can mean a love affair)
'love in a rum setting' is the wordplay.
'love' becomes 'o' (love means zero in tennis).
'in' is an insertion indicator.
'setting' is an anagram indicator.
'a'+'rum'='arum'
'arum' anagrammed gives 'amur'.
'o' going inside 'amur' is 'AMOUR'.
'of' acts as a link.
(Other definitions for amour that I've seen before include "(Secret) lover" , "Loved one (French)" , "Affaire" , "Romantic affair" , "Fling" .)