Causing injury to dog, commonly in flank (8)
I believe the answer is:
wounding
'causing injury to' is the definition.
(to wound someone is to cause an injury)
'dog commonly in flank' is the wordplay.
I cannot quite understand how this works, but
'in' is within the answer.
This may be the basis of the clue (or it may be nonsense).
(Other definitions for wounding that I've seen before include "Injuring" , "painful" , "Maiming, harming" .)