Judge to support dismissing British sailor (4)
I believe the answer is:
jack
'sailor' is the definition.
(thesaurus)
'judge to support dismissing british' is the wordplay.
'judge' becomes 'j'.
'to support' becomes 'back' (back is a kind of support).
'dismissing' suggests deleting specific letters.
'british' becomes 'b' (abbreviation e.g. in 'BBC').
'back' with 'b' taken away is 'ack'.
'j'+'ack'='JACK'
(Other definitions for jack that I've seen before include "-- Sprat; -- Horner" , "Sort of boot, hammer, pot or tar" , "elevator?" , "Card -- raiser" , "Raising device, socket" .)