Johnson in tribute offers high-level support for sailors (7)
I believe the answer is:
topmast
'high-level support for sailors' is the definition.
'johnson in tribute' is the wordplay.
'johnson' becomes 'pm' (Boris Johnson, Prime Minister).
'in' indicates putting letters inside.
'tribute' becomes 'toast' (I've seen this before).
'pm' going inside 'toast' is 'TOPMAST'.
'offers' is the link.
(Other definitions for topmast that I've seen before include "Sail up here" , "Most apt (anag) - feature of a square-rigged ship" , "High part of sailing ship" , "Sail-supporting section of a ship" , "high post" .)