A northern bird behind large light (7)
I believe the answer is:
lantern
'light' is the definition.
(lantern is a type of light)
'a northern bird behind large' is the wordplay.
'a' becomes 'an'.
'northern bird' becomes 'tern' (tern is a kind of bird. I am not sure about the 'northern' bit.).
'behind' says to put letters next to each other.
'large' becomes 'L' (eg in clothes sizes).
'an'+'tern'='antern'
'antern' put after 'l' is 'LANTERN'.
Can you help me to learn more?
(Other definitions for lantern that I've seen before include "Case for a light, provides pictures when magic" , "Enclosed lamp" , "Cased lamp" , "It illuminates" , "Light in a transparent protective case" .)