Great stuff Chris. Didn't take you long once a few paltry letters were supplied. I never guessed they'd prove to be so challenging this week. I'm secretly delighted, of course :)
Here is my working. I wonder if you'll think no. 3 is a "self-kicker"? Here goes:-
1. subtractive anag (from & representation) of “elected MPs bars” – “ accepted” = RESEMBLES = favours.
2. A = a; flat = boring (flat = boring and boring = flat in Chambers and Oxford thesauri); nitrogen = N; yielding; a bor(N)ing = ABORNING = aborning (US) [adv] = while being produced (Chambers D)
3. (crypt) (m)ADMAN = he plays a part in promoting
4. opening = pore; back opening = erop; a way = a lane; a(erop)lane = AEROPLANE = a flier.
5. (charade). about = c; mother = ma; whip = lash; a beginner = L; underground explorers = cavers. c(lash) ma c(L)avers = CLASH-MA-CLAVERS = gossip (Chambers Dict).