I mean to arrange that the dog goes in for treatment (8)
I believe the answer is:
manicure
'treatment' is the definition.
(nail treatment)
'i mean to arrange that the dog goes in' is the wordplay.
'to arrange' indicates an anagram.
'that the dog' becomes 'cur' (a cur is an aggressive or scruffy dog).
'goes in' is an insertion indicator.
'i'+'mean'='imean'
'imean' with letters rearranged gives 'manie'.
'manie' enclosing 'cur' is 'MANICURE'.
'for' is the link.
(Other definitions for manicure that I've seen before include "Work on hand" , "Professional care for the hands" , "attention to extremities" , "Trim" , "Grooming for 10, 17 and 18" .)