In the cinema, maybe, he's concerned with hard water (6)
I believe the answer is:
iceman
'he's concerned with hard water' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
'in the cinema' is the wordplay.
'cinema' can be anagrammed to 'ICEMAN'.
However, I'm not clear how the anagram is indicated.
'maybe' acts as a link.
Can you help me to learn more?
(Other definitions for iceman that I've seen before include "Cold character in cinema" , "Professional killer - jewel thief - Eugene O'Neill character" , "assassin" , "Eugene O'Neill's figure of 'death' (the one who cometh!)" , "He delivers" .)