Left behind end of extension for sun lamp (7)
I believe the answer is:
lantern
'sun lamp' is the definition.
'lantern' can be an answer for 'lamp' (lantern is a kind of lamp). I'm unsure of the 'sun' bit.
'left behind end of extension for' is the wordplay.
'left' becomes 'l' (common abbreviation).
'behind' becomes 'astern' (at the back or behind of a ship).
'end of' says to hollow out the word (remove centre letters) (I've seen 'ends' mean this).
'extension for' becomes 'tern' (I can't justify this - if you can you should give a lot more credence to this answer).
'astern' with its middle taken out is 'an'.
'l'+'an'+'tern'='LANTERN'
Can you help me to learn more?
(Other definitions for lantern that I've seen before include "Light in a protective casing" , "Lamp with protective transparent casing" , "Portable lamp case" , "Leading light" , "Enclosed lamp" .)