Dillydallies (4)
I believe the answer is:
lags
'dillydallies' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for lags that I've seen before include "Fails to keep up" , "Slows down and falls behind" , "Dawdles" , "Hangs back" , "Delays" .)