Some exploit ertswhile lags (7)
I believe the answer is:
loiters
'lags' is the definition.
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for loiters that I've seen before include "Waits idly" , "Hangs about with toilers" , "Fails to move on" , "Hangs about idly" , "dawdles" .)