Extra for packet? More than enough soup without seconds (6,7)

I haven't cracked this one yet — but the brilliant team at Times for the Times have:

EXCESS (more than enough) S (seconds) in POTAGE (soup); excess postage is essentially the payment due from the addressee when insufficient stamps have been put on a letter or packet. I put first ‘excess luggage’, then ‘excess baggage’, each of which, unlike ‘excess postage’, has its own entry in Collins.