Painful injury resulting from run in country (6)
I believe the answer is:
sprain
'painful injury' is the definition.
(type of injury)
'run in country' is the wordplay.
'run' becomes 'r' (cricket abbreviation).
'in' means one lot of letters goes inside another.
'country' becomes 'spain' (Spain is an example).
'r' going inside 'spain' is 'SPRAIN'.
'resulting from' is the link.
(Other definitions for sprain that I've seen before include "Pull" , "unwelcome twist" , "Wrench (an ankle) 6)" , "Wrench (limb)" , "Turn" .)