Purely symbolic number approved for inclusion (5)
I believe the answer is:
token
'purely symbolic' is the definition.
(as in a token gesture)
'number approved for inclusion' is the wordplay.
'number' becomes 'ten' (ten is a kind of number).
'approved' becomes 'ok' (I've seen this in other clues).
'for inclusion' indicates putting letters inside.
'ten' enclosing 'ok' is 'TOKEN'.
(Other definitions for token that I've seen before include "Privately issued coin or voucher" , "Emblem" , "Keepsake or memorial as of friendship" , "signal" , "without meaning it" .)