Pull or drag with effort (4)
I believe the answer is:
haul
I believe this clue is a double definition.
'pull' is the first definition.
(I know that haul is a type of pull)
'drag with effort' is the second definition.
(I've seen this before)
(Other definitions for haul that I've seen before include "Draw slowly or heavily" , "Lug -- proceeds of robbery" , "Drag along behind" , "Drag; booty" , "Drag (something heavy)" .)