Drag, pull with effort (4)
I believe the answer is:
haul
I believe this clue is a double definition.
'drag' is the first definition.
(I know that drag can be written as haul)
'pull with effort' is the second definition.
(I've seen this in another clue)
(Other definitions for haul that I've seen before include "Drag along behind" , "TRICK/TRICE" , "Pull along behind" , "Pull forcibly; catch" , "Draw slowly or heavily" .)