Promise, if thou bringest home the bacon! (7)
I believe the answer is:
earnest
'promise' is the definition.
(I've seen this before)
'thou bringest home the bacon' is the wordplay.
I cannot really understand how this works, but
'home' could be 'nest' (a bird's home) and 'nest' is found within the answer.
The remaining letters 'ear' is a valid word which might be clued in a way I don't understand.
This may be the basis of the clue (or it may be nonsense).
'if' is the link.
Can you help me to learn more?
(Other definitions for earnest that I've seen before include "Serious - money deposit" , "art collector" , "Sincere; determined" , "Fixed" , "Sincere in intention" .)