Fifty reunited in resort for a spell (9)
I believe the answer is:
interlude
'a spell' is the definition.
(thesaurus)
'fifty reunited in resort' is the wordplay.
'fifty' becomes 'L' (Roman numeral).
'in resort' indicates anagramming the letters (the letters are re-sorted).
'l'+'reunited'='lreunited'
'lreunited' is an anagram of 'INTERLUDE'.
'for' acts as a link.
(Other definitions for interlude that I've seen before include "Space of time; break" , "Break in performance" , "Eli turned (anag.)" , "Temporary amusement or diversion" , "Hiatus" .)