Pound back on hot dog (5)
I believe the answer is:
pooch
'dog' is the definition.
(I know that pooch is a type of dog)
'pound back on hot' is the wordplay.
'pound' becomes 'coop' (I've seen this before).
'back' says the letters should be written in reverse.
'on' means one lot of letters go next to another.
'hot' becomes 'h' (abbreviation eg on taps).
'coop' backwards is 'pooc'.
'pooc'+'h'='POOCH'
(Other definitions for pooch that I've seen before include "Doggy" , "Dog (colloq.)" , "one of our best friends" .)