Portion, instalment (7)
I believe the answer is:
tranche
This clue is a double definition.
'portion' is the first definition.
(I know that tranche is a type of portion)
'instalment' is the second definition.
(I've seen this before)
(Other definitions for tranche that I've seen before include "Portion of something, money perhaps" , "Share -- chanter (anag)" , "batch supplied" , "Instalment of e.g. loan" , "Part or block of something" .)