Friend throughout the year (4)
I believe the answer is:
ally
'friend' is the definition.
(an ally is a friend or supporter)
'throughout the year' is the wordplay.
'throughout' becomes 'all' (I can't justify this - if you can you should believe this answer much more).
'the year' becomes 'y'.
'all'+'y'='ALLY'
Can you help me to learn more?
(Other definitions for ally that I've seen before include "Friend in time of need" , "One on one's side" , "Friend and colleague" , "Crony" , "A friendly and reliable country" .)