Current to change, yet Deighton starts emitting welding gas? (9)
I believe the answer is:
acetylene
'welding gas?' is the definition.
(I've seen this before)
'current to change yet deighton starts emitting' is the wordplay.
'current' becomes 'ac' (alternating current).
'to change' indicates anagramming the letters.
'deighton' becomes 'len' (I've seen this in another clue).
'starts' suggests taking the first letters.
The initial letter of 'emitting' is 'e'.
'yet' is an anagram of 'ety'.
'ac'+'ety'+'len'+'e'='ACETYLENE'
(Other definitions for acetylene that I've seen before include "powers industrial torch" , "cutting gas emission?" , "Gas used chiefly in welding" , "Illuminating stuff also used for joining" , "Flammable gas" .)