Say thanks for the salt (3)
I believe the answer is:
tar
'salt' is the definition.
(both can informally mean a sailor)
'say thanks' is the wordplay.
'say' indicates a 'sounds like' (homophone) clue.
'thanks' becomes 'ta' (UK informal version of 'thank you').
'ta' is a homophone of 'TAR'.
'for the' is the link.
(Other definitions for tar that I've seen before include "Black coat" , "one may need to pay on boat" , "Flammable liquid; sailor" , "Viscous mixture - sailor" , "Thick, sticky liquid distilled from coal" .)