The first clue to the solution is: Substance in tobacco reinforces addiction (4)
It may be a hidden word in the clue, i.e. CORE. But I cannot parse it. Is it indeed CORE or could be something else?
The second clue is: Bare-backed in abbreviated underwear (4)
I cannot figure out what it can be, but the last letter is the same as the last letter of the first clue.
Anyone can help, please?