Engineers flag and stop working (6)
I believe the answer is:
retire
'stop working' is the definition.
(retiring from work)
'engineers flag' is the wordplay.
'engineers' becomes 're' (abbreviation for Royal Engineers).
'flag' becomes 'tire' (both can mean to become weary).
're'+'tire'='RETIRE'
'and' acts as a link.
(Other definitions for retire that I've seen before include "end occupation" , "climb the stairs" , "Leave job permanently (6)" , "Give up working and go to bed" , "Withdraw from active participation" .)