Stiff arms, having to cultivate (4)
I believe the answer is:
farm
'to cultivate' is the definition.
(I know this)
'stiff arms having' is the wordplay.
'having' indicates the answer is hidden within the clue.
'FARM' can be found hidden inside 'stiff arms'.
(Other definitions for farm that I've seen before include "Agricultural unit" , "Smallholding" , "Ranch" , "Old MacDonald's establishment" , "Rural workplace" .)