King, say, starts to exhibit neurotic tendencies? I may act for him (6)
I believe the answer is:
regent
'king say starts to exhibit neurotic tendencies? i may act for him' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition. I also know that 'king' relates to this answer.
'king say starts to exhibit neurotic tendencies?' is the wordplay.
'king' becomes 'r' (r is abbreviation for rex).
'say' becomes 'eg'.
'starts to' says to take the initial letters.
The first letters of 'exhibit neurotic tendencies' is 'ent'.
'r'+'eg'+'ent'='REGENT'
(Other definitions for regent that I've seen before include "being temporarily in charge" , "Queen possibly" , "Not quite king" , "Acting ruler" , "Person appointed as acting monarch" .)