Seafood, we hear, will provide strength (6)
I believe the answer is:
muscle
'strength' is the definition.
(muscle can mean strength or force)
'seafood we hear' is the wordplay.
'seafood' becomes 'mussel' (mussel is a kind of seafood).
'we hear' shows a homophone (sound like).
'mussel' is a homophone of 'MUSCLE'.
'will provide' acts as a link.
(Other definitions for muscle that I've seen before include "Fibrous tissue in the body" , "Body tissue that affects movement" , "Beef" , "for bearing around?" , "Body tissue that effects movement" .)