Either way it's essential to a helicopter (5)
I believe the answer is:
rotor
'either way' is the definition.
'it's essential to a helicopter' is the wordplay.
'it's' becomes 'roto' (I am not sure about this - if you are sure you should believe this answer much more).
'essential to' indicates the central letters.
'a helicopter' becomes 'cargo' (cargo helicopter is a kind of helicopter).
The centre of 'cargo' is 'r'.
'roto'+'r'='ROTOR'
Can you help me to learn more?
(Other definitions for rotor that I've seen before include "Palindromic moving part" , "Revolving part of machinery" , "Helicopter propeller" , "Revolving arm in machine" , "Helicopter vane" .)