Refuse to deal with sailor showing pirate's flag (9)
I believe the answer is:
blackjack
'pirate's flag' is the definition.
'refuse to deal with sailor' is the wordplay.
'refuse to deal with' becomes 'black' (type of industrial action in the UK).
'sailor' becomes 'jack' (I've seen this before).
'black'+'jack'='BLACKJACK'
'showing' acts as a link.
(Other definitions for blackjack that I've seen before include "Casino card game" , "Vingt-et-un - pirates' ensign" , "2 8 [CASINO GAME]" , "Club" , "Gambling card game" .)