Ten is about acceptable as a symbol (5)
I believe the answer is:
token
'a symbol' is the definition.
(token is a kind of symbol)
'ten is about acceptable' is the wordplay.
'is about' means one lot of letters goes inside another.
'acceptable' becomes 'OK' (OK can mean acceptable or fine).
'ten' enclosing 'ok' is 'TOKEN'.
'as' acts as a link.
(Other definitions for token that I've seen before include "signal" , "Symbolic; voucher" , "Badge; voucher" , "Counter" , "Done only as a symbolic gesture" .)