Number pass inside producing voucher (5)
I believe the answer is:
token
'voucher' is the definition.
(I've seen this before)
'number pass inside' is the wordplay.
'number' becomes 'ten' (ten is a kind of number).
'pass' becomes 'ok' (oking is a kind of passing).
'inside' is an insertion indicator.
'ten' going around 'ok' is 'TOKEN'.
'producing' acts as a link.
(Other definitions for token that I've seen before include "Done for appearance's sake" , "signal" , "Voucher (for, eg, books)" , "Plastic coin substitute" , "Representative item" .)