Hot fish, pleasant, lacking one sauce (9)
I believe the answer is:
insolence
'sauce' is the definition.
(thesaurus)
'hot fish pleasant lacking one' is the wordplay.
'hot' becomes 'in' (both can mean fashionable).
'fish' becomes 'sole' (I've seen this before**).
'pleasant' becomes 'nice' ('nice' is associated in meaning with 'pleasant').
'lacking' is a deletion indicator.
'one' becomes 'i' (Roman numeral).
'nice' with 'i' removed is 'nce'.
'in'+'sole'+'nce'='INSOLENCE'
(Other definitions for insolence that I've seen before include "Sauce" , "Rudeness, disrespect" , "Rude behaviour" , "Rudeness, impudence" , "Lip; cheek" .)