Dog to retire — will take some rest (7)
I believe the answer is:
terrier
'dog' is the definition.
(terrier is a kind of dog)
'retire will take some rest' is the wordplay.
I cannot really see how this works, but
an anagram of 'retire' is 'terrie' which is within the answer.
'take' could be 'r' (abbreviation for 'recipe', Latin for 'take') and 'r' is located in the answer.
No letters remain.
This explanation may well be incorrect...
'to' acts as a link.
Can you help me to learn more?
(Other definitions for terrier that I've seen before include "Sealyham, for example" , "he's not a boxer" , "Dog - old land register" , "Dog originally used to ferret out burrowing animals" , "Reserve soldier" .)