The dog sank her teeth into a companion! (5)
I believe the answer is:
bitch
'the dog' is the definition.
(I've seen this before)
'sank her teeth into a companion' is the wordplay.
I cannot quite understand how this works, but
'companion' could be 'ch' (Companion of Honour) and 'ch' is present in the answer.
The remaining letters 'bit' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for bitch that I've seen before include "grouse" , "Retriever likely to drop" , "Female dog" , "Female animal" , "Malicious woman" .)