Rise in allowance taking long? (8)
I believe the answer is:
gradient
'rise' is the definition.
(I've seen this before)
'allowance taking long?' is the wordplay.
'allowance' becomes 'grant' (both can mean money given to someone).
'taking' indicates putting letters inside.
'long?' becomes 'die' (to long for or to die for something is to crave it).
'grant' placed around 'die' is 'GRADIENT'.
'in' acts as a link.
(Other definitions for gradient that I've seen before include "Angle of slope" , "Bank" , "Slope or incline" , "Rise" , "Third OT book" .)