Number receiving satisfactory sign (5)
I believe the answer is:
token
'sign' is the definition.
(I know that token is a type of sign)
'number receiving satisfactory' is the wordplay.
'number' becomes 'ten' (ten is a kind of whole number).
'receiving' means one lot of letters goes inside another.
'satisfactory' becomes 'ok' (similar in meaning).
'ten' going around 'ok' is 'TOKEN'.
(Other definitions for token that I've seen before include "Badge; voucher" , "Gift voucher - symbol" , "signal" , "Voucher (for, eg, books)" , "empty gesture?" .)