Payment hard old woman initially invested in drink (10)
I believe the answer is:
honorarium
'payment' is the definition.
(honorarium is a kind of payment)
'hard old woman initially invested in drink' is the wordplay.
'hard old woman' becomes 'honora' (I can't explain this - if you can you should believe this answer much more).
'initially' indicates taking the first letters.
'in' indicates putting letters inside.
'drink' becomes 'rum' (rum is a kind of drink).
The initial letter of 'invested' is 'i'.
'i' going within 'rum' is 'rium'.
'honora'+'rium'='HONORARIUM'
(Another definition for honorarium that I've seen is " Nominal payment for professional services".)