Reject papers turned yellowish (8)
I believe the answer is:
disallow
'reject' is the definition.
(I've seen this before)
'papers turned yellowish' is the wordplay.
'papers' becomes 'ID' (identifying documents are one's 'papers').
'turned' says the letters should be written backwards.
'yellowish' becomes 'sallow' (I've seen this before).
'id' written backwards gives 'di'.
'di'+'sallow'='DISALLOW'
(Other definitions for disallow that I've seen before include "Refuse to accept as valid, as judge might a claim" , "Reject" , "Prevent" , "Prohibit, veto" , "refuse permission" .)