Work at steadily; fold (3)
I believe the answer is:
ply
This clue is a double definition.
'work at steadily' is the first definition.
(I've seen this in another clue)
'fold' is the second definition.
(I've seen this before)
(Other definitions for ply that I've seen before include "Work steadily as at one's trade" , "drama one's missed" , "'Persist in offering, liquor say (3)'" , "Work steadily at, say trade" , "carry on" .)