Man’s cosy home descended on by queen (6)
I believe the answer is:
ernest
'man's' is the definition.
(man's name)
'cosy home descended on by queen' is the wordplay.
'cosy home' becomes 'nest'.
'descended on by' says to put letters next to each other (in a down clue, some letters descend onto others).
'queen' becomes 'ER' (abbreviation for Elizabeth Regina).
'nest' after 'er' is 'ERNEST'.
(Other definitions for ernest that I've seen before include "Author Hemmingway, and Oscar Wilde's hero" , "chap" , "Name beloved of Gwen Fairfax (Wilde)" , "Resent (anag) - man" , "Male" .)