Service charge offered regularly (3)
I believe the answer is:
fee
'service charge' is the definition.
(I've seen this in another clue)
'offered regularly' is the wordplay.
'regularly' means one should take alternating letters (regularly take one letter, leave next etc.).
The alternate letters of 'offered' are 'FEE'.
(Other definitions for fee that I've seen before include "Cost" , "price" , "Money paid for professional services" , "Sum payable to, say, barrister" , "(Entry) charge" .)