Record quiet increase in business (10)
I believe the answer is:
enterprise
'business' is the definition.
(thesaurus)
'record quiet increase' is the wordplay.
'record' becomes 'enter' ('enter' can be a synonym of 'record').
'quiet increase' becomes 'prise' (I can't explain this - if you can you should give a lot more credence to this answer).
'enter'+'prise'='ENTERPRISE'
'in' acts as a link.
Can you help me to learn more?
(Other definitions for enterprise that I've seen before include "Initiative - undertaking - business" , "Bold resourcefulness" , "Get-up-and-go - venture" , "business concern" , "Company" .)