Did he become immortal by looking both ways? (5)
I believe the answer is:
janus
'immortal by looking both ways?' is the definition.
The definition suggests a singular noun which matches the answer.
'did he' is the wordplay.
I cannot really understand how this works, but
'he' could be 'jan' and 'jan' is found in the answer.
The remaining letters 'us' is a valid word which might be clued in a way I don't see.
This may be the basis of the clue (or it may be nonsense).
'become' acts as a link.
Can you help me to learn more?
(Other definitions for janus that I've seen before include "Two-faced person" , "Two-faced god of gates and doors - Guardian cryptic crossword setter" , "Roman god of doors and beginnings" , "Roman god of doors, usually two-faced - a month is named for him" , "Roman deity who faces front and back" .)