Portion of mackerel I shall look forward to (6)
I believe the answer is:
relish
'look forward to' is the definition.
(thesaurus)
'portion of mackerel i shall' is the wordplay.
'portion of' indicates a hidden word.
'RELISH' can be found hidden inside 'mackerel i shall'.
(Other definitions for relish that I've seen before include "Piquant sauce or pickle" , "Enjoy greatly - such sauce!" , "Savour an experience" , "smack" , "Thoroughly enjoy" .)