Sailor's newspaper leading on a Spanish seaport (9)
I believe the answer is:
tarragona
'spanish seaport' is the definition.
The definition suggests a singular noun which matches the answer.
'sailor's newspaper leading on a' is the wordplay.
'sailor' becomes 'tar' (slang term for a sailor).
'newspaper' becomes 'rag' (informal term for a newspaper).
'leading' says to put letters next to each other.
'tar'+'rag'+'on'+'a'='TARRAGONA'
Can you help me to learn more?
(Other definitions for tarragona that I've seen before include "port, in Spain" , "Spanish wine" , "Spanish port" , "Spanish city" , "Spanish province" .)