Youth, cold, greeting lord with head covering (9)
I believe the answer is:
childhood
'youth' is the definition.
(I've seen this before)
'cold greeting lord with head covering' is the wordplay.
'cold' becomes 'C' (eg on taps).
'greeting' becomes 'hi' (hi is a kind of greeting).
'lord' becomes 'ld' (abbreviation for the aristocratic title).
'with' says to put letters next to each other.
'head covering' becomes 'hood' (I've seen this in another clue).
'c'+'hi'+'ld'+'hood'='CHILDHOOD'
(Other definitions for childhood that I've seen before include "Young state" , "Early years" , "Extreme youth" , "Time of immaturity" , "Between infancy and adolescence" .)