Meat reserve supplies seaport (9)
I believe the answer is:
liverpool
'seaport' is the definition.
The answer and definition can be both locations as well as being singular nouns.
Perhaps they are linked in a way I don't understand?
'meat reserve' is the wordplay.
'meat' becomes 'liver' (liver is a kind of meat).
'reserve' becomes 'pool' (pool is a kind of reserve).
'liver'+'pool'='LIVERPOOL'
'supplies' acts as a link.
Can you help me to learn more?
(Other definitions for liverpool that I've seen before include "city with two cathedrals" , "team" , "Where Beatles started" , "Side" , "Merseyside city of The Beatles" .)