In high spirits and nubile? Let loose! (9)
I believe the answer is:
ebullient
'in high spirits' is the definition.
(I've seen this in another clue)
'nubile? let loose' is the wordplay.
'loose' is an anagram indicator (letters are loosened from their original positions).
'nubile'+'let'='nubilelet'
'nubilelet' anagrammed gives 'EBULLIENT'.
'and' is the link.
(Other definitions for ebullient that I've seen before include "Full of cheerful enthusiasm" , "High-spirited - exhilarated" , "Overflowing with enthusiasm" , "Joyously unrestrained" , "Libel tune (anag.)" .)