Collieries about to terminate regular pay (7)
I believe the answer is:
stipend
'regular pay' is the definition.
(a stipend is a regular payment)
'collieries about to terminate' is the wordplay.
'collieries' becomes 'pits' ('pit' can be a synonym of 'colliery').
'about' says the letters should be written backwards.
'to terminate' becomes 'end' ('end' can be a synonym of 'terminate').
'pits' back-to-front is 'stip'.
'stip'+'end'='STIPEND'
(Other definitions for stipend that I've seen before include "Soldier's pay" , "Periodical allowance" , "Payment for cleric" , "Clerical salary" , "Minister's salary" .)