Mapmakers interrupted by recall of finished work (4)
I believe the answer is:
opus
'work' is the definition.
(an opus is an artistic work)
'mapmakers interrupted by recall of finished' is the wordplay.
'mapmakers' becomes 'OS' (Ordnance Survey).
'interrupted by' is an insertion indicator.
'recall of' shows that the letters should be reversed in order.
'finished' becomes 'up' (eg 'time's up' means the time is finished).
'up' backwards is 'pu'.
'os' going around 'pu' is 'OPUS'.
(Other definitions for opus that I've seen before include "Work or composition, usually musical" , "Composition - magnum __" , "Work of 25 perhaps" , "Musical piece" , "Work (mus.)" .)