Turn up at long last with a dog (3)
I believe the answer is:
pug
'a dog' is the definition.
(pug is a kind of dog)
'turn up at long last' is the wordplay.
'turn' shows that the letters should be reversed in order.
'at' is a charade indicator (letters next to each other).
'last' says to take the final letters.
The final letter of 'long' is 'g'.
'up' back-to-front is 'pu'.
'pu'+'g'='PUG'
'with' acts as a link.
(Other definitions for pug that I've seen before include "A dog; pack with clay" , "Small boxer" , "Flat-nosed dog breed" , "Dog with broad flat nose, or an informal boxer" , "Small dog with flat nose and wrinkled face" .)