A redhead with higher energy going grey? (6)
I believe the answer is:
ageing
'going grey?' is the definition.
(someone might go grey as they age)
'a redhead with higher energy' is the wordplay.
'redhead' becomes 'ging' (I am not sure about this - if you are sure you should believe this answer much more).
'with' indicates putting letters inside.
'higher' suggests taking the first letters (I've seen 'highest of' mean this (top letter - down clues only)).
The initial letter of 'energy' is 'e'.
'ging' enclosing 'e' is 'geing'.
'a'+'geing'='AGEING'
Can you help me to learn more?
(Other definitions for ageing that I've seen before include "Getting old" , "Growing old" , "Getting older" , "Declining" , "getting more advanced?" .)