Gas etc exploded, getting unknown man in A&E (9)
I believe the answer is:
acetylene
'gas' is the definition.
(I've seen this before)
'etc exploded getting unknown man in ae' is the wordplay.
'exploded' indicates anagramming the letters.
'getting' is a charade indicator (letters next to each other).
'unknown' becomes 'y' (algebra).
'man' becomes 'len' (I've seen this in other clues**).
'in' indicates putting letters inside.
'etc' anagrammed gives 'cet'.
'cet'+'y'+'len'='cetylen'
'cetylen' placed into 'ae' is 'ACETYLENE'.
(Other definitions for acetylene that I've seen before include "powers industrial torch" , "Illuminating stuff also used for joining" , "Flammable gas" , "cutting gas emission?" , "Gas used chiefly in welding" .)