Overwhelming quantity to carry and harbour (7)
I believe the answer is:
seaport
'harbour' is the definition.
(synonyms)
'overwhelming quantity to carry' is the wordplay.
'overwhelming quantity' becomes 'sea' (sea is a kind of quantity. I am not sure about the 'overwhelming' bit.).
'to carry' becomes 'port' (porting is a kind of carrying).
'sea'+'port'='SEAPORT'
'and' is the link.
Can you help me to learn more?
(Other definitions for seaport that I've seen before include "Place with harbour for ocean-going ships" , "access to drink" , "place on the coast" , "Embarkation and disembarkation point for ocean-going ships" , "Town with a large harbour" .)