Sodium battery covers energy for part of aircraft (7)
I believe the answer is:
nacelle
'part of aircraft' is the definition.
'nacelle' can be an answer for 'part' (I have seen 'part of Jumbo' mean 'nacelle' so perhaps 'part' could also mean 'nacelle'). I am not sure about the 'of aircraft' bit.
'sodium battery covers energy for' is the wordplay.
'sodium' becomes 'na' (chemical symbol).
'battery' becomes 'c' (C battery is an example).
'covers' means one lot of letters go next to another.
'energy for' becomes 'elle' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'na'+'c'+'elle'='NACELLE'
Can you help me to learn more?
(Other definitions for nacelle that I've seen before include "airship's gondola" , "part of Jumbo" , "Aircraft engine casing" , "Streamlined housing on an aircraft" , "Streamlined cover for an aircraft engine" .)