Turn up without prohibition for old Japanese coin (5)
I believe the answer is:
obang
'old japanese coin' is the definition.
(I've seen this before)
'turn up without prohibition' is the wordplay.
'turn' becomes 'go' (a person's move in a board game).
'up' says the letters should be written backwards (in down clue: letters go upwards).
'without' indicates putting letters inside ('without' can be similar in meaning to 'outside').
'prohibition' becomes 'ban' (synonyms).
'go' reversed gives 'og'.
'og' going around 'ban' is 'OBANG'.
'for' acts as a link.
(Another definition for obang that I've seen is " Old Japanese oblong gold coin".)