PS: on reflection, wet weather can cause injury (6)
I believe the answer is:
sprain
'injury' is the definition.
(I know that sprain is a type of pull)
'ps on reflection wet weather' is the wordplay.
'on reflection' shows that the letters should be reversed in order.
'wet weather' becomes 'rain' (rain is wet weather).
'ps' backwards is 'sp'.
'sp'+'rain'='SPRAIN'
'can cause' acts as a link.
(Other definitions for sprain that I've seen before include "Wrench (an ankle) 6)" , "Wrench, dislocate" , "Wrench (ligaments)" , "Twist ligament(s)" , "Wrench; in rasp (anag.)" .)