He and CO seen together, symbolic of what? (5)
I believe the answer is:
gases
'co seen together symbolic of what?' is the definition.
I can't tell whether this defines the answer.
'he' is the wordplay.
I cannot really see how this works, but
'he' could be 'ase' and 'ase' is present in the answer.
This may be the basis of clue (or it may be nonsense).
'and' acts as a link.
Can you help me to learn more?
(Other definitions for gases that I've seen before include "Such as radon and neon" , "Air-like fluids" , "Cruelly kills" , "Eg, oxygen, helium" , "Neon, oxygen, etc" .)