Nookie, say, occasionally ear-splitting (5)
I believe the answer is:
noisy
'ear-splitting' is the definition.
(thesaurus)
'nookie say occasionally' is the wordplay.
'occasionally' means one should take alternating letters (letters taken at regular intervals or occasions).
'nookie'+'say'='nookiesay'
The alternating letters of 'nookiesay' are 'NOISY'.
(Other definitions for noisy that I've seen before include "row" , "Making much sound" , "Clamorous" , "Rowdy" , "Vocal" .)