Transmit clue hidden inside for a small fee (7)
I believe the answer is:
stipend
'for a small fee' is the definition.
(a small sum paid regularly to someone)
'transmit clue hidden' is the wordplay.
'transmit' becomes 'send' (sending is a kind of transmiting).
'clue' becomes 'tip' (I've seen this before).
'hidden' means one lot of letters goes inside another.
'send' enclosing 'tip' is 'STIPEND'.
'inside' acts as a link.
(Other definitions for stipend that I've seen before include "Payment for cleric" , "Sum of money" , "Salary, allowance" , "Minister's salary" , "Official income of Protestant clergyman" .)