Soldier sat on by my dog (5)
I believe the answer is:
corgi
'dog' is the definition.
(corgi is a kind of dog)
'soldier sat on by my' is the wordplay.
'soldier' becomes 'gi' (government issue or general issue).
'sat on by' means one lot of letters go next to another.
'my' becomes 'cor' (I've seen this in other clues).
'gi' after 'cor' is 'CORGI'.
(Other definitions for corgi that I've seen before include "Queen likes this" , "Cardigan or Pembroke dog" , "Royal canine" , "The Queen's favourite?" , "Welsh breed of short-legged dog" .)