Announce it's for the shellfish I am stuffing (8)
I believe the answer is:
proclaim
'announce' is the definition.
(thesaurus)
'for the shellfish i am stuffing' is the wordplay.
'for' becomes 'pro' (I've seen this before**).
'the shellfish' becomes 'clam' (clam is a kind of shellfish).
'i am' becomes 'i' (I've seen this in other clues).
'stuffing' is an insertion indicator.
'clam' placed around 'i' is 'claim'.
'pro'+'claim'='PROCLAIM'
'it's' is the link.
(Other definitions for proclaim that I've seen before include "Herald" , "Broadcast" , "advertise" , "Speak out" , "Announce officially or declare publicly" .)