Seafood provides strength, we hear (6)
I believe the answer is:
mussel
'seafood' is the definition.
(mussel is a kind of seafood)
'strength we hear' is the wordplay.
'strength' becomes 'muscle' (muscle is a kind of strength).
'we hear' shows a homophone (sound like).
'muscle' is a homophone of 'MUSSEL'.
'provides' is the link.
(Other definitions for mussel that I've seen before include "Edible shellfish" , "Edible bivalve mollusc, common in sea" , "Edible marine mollusc sold by Molly Malone - not the cockle" , "Type of shellfish" , "Common bivalve shellfish, anchors to rocks" .)