12. This device was used to measure electrical resustance and is named surprisingly, not after the inventor, after the man who promoted it's use. 1st word = surname (uncommon). Before grid entry adjustment, an anagram of et (left regularly censored) + wing broadsheet + a.
14. Press as in the media.
I think I now have the 2 twelve letter words so know which letters are missing - 4 left to go 1A, 6A,10A and 17D. 2D is really annoying - don't think I'll get 6A.
1a think type of exercise at the gym
6a type of acupressure/massage
10a physics or chemistry would have been a bigger help in the clue
17d further def: annoying/boring
2d fat (or fattish) is the defn