Bring to light furnace regularly in the past (7)
I believe the answer is:
uncover
'bring to light' is the definition.
(I've seen this in another clue)
'furnace regularly in the past' is the wordplay.
'regularly' indicates alternate letters (regularly take one letter, leave next etc.).
'in the past' becomes 'over' (both can mean finished or completed).
The alternate letters of 'furnace' are 'unc'.
'unc'+'over'='UNCOVER'
(Other definitions for uncover that I've seen before include "Expose, reveal" , "Strip off" , "Take the lid off" , "make a revelation" , "Make visible" .)