Ruling on posh chap? (6)
I believe the answer is:
regent
'ruling' is the definition.
(I've seen this before)
'on posh chap?' is the wordplay.
'on' becomes 're' (regarding).
'posh chap?' becomes 'gent' (both can mean a man. I am not sure about the 'posh' bit.).
're'+'gent'='REGENT'
Can you help me to learn more?
(Other definitions for regent that I've seen before include "One acting for monarch who is a minor" , "Interim monarch" , "Someone ruling on behalf of another" , "Acting ruler" , "Stand-in monarch" .)