Person revered by one pretty girl mostly (4)
I believe the answer is:
idol
'person revered' is the definition.
'by one pretty girl mostly' is the wordplay.
'by' says to put letters next to each other.
'one' becomes 'i' (Roman numeral).
'pretty girl' becomes 'doll'.
'mostly' means to remove the last letter.
'doll' with its last letter removed is 'dol'.
'i'+'dol' is 'IDOL'.
(Other definitions for idol that I've seen before include "Darling" , "Who's greatly respected" , "Effigy" , "Something worshipped" , "Worshipped image; lido (anag.)" .)