Man's best friend gets to slip in part of a stand (7)
I believe the answer is:
terrier
'man's best friend' is the definition.
(type of dog)
'slip in part of a stand' is the wordplay.
'slip' becomes 'err' (to err is to make an error).
'in' indicates putting letters inside.
'part of a stand' becomes 'tier' (I can't explain this - if you can you should give a lot more credence to this answer).
'err' placed inside 'tier' is 'TERRIER'.
'gets to' acts as a link.
Can you help me to learn more?
(Other definitions for terrier that I've seen before include "Reserve soldier" , "part-timer in Services" , "Dog - reservist" , "Persistent person" , "Dog - army volunteer - land register" .)