Squeeze, essentially arm in arm (5)
I believe the answer is:
wring
'squeeze' is the definition.
(synonyms)
'essentially arm in arm' is the wordplay.
'essentially' indicates the central letters.
'in' is an insertion indicator.
'arm' becomes 'wing' (I can't explain this - if you can you should believe this answer much more).
The middle of 'arm' is 'r'.
'r' put into 'wing' is 'WRING'.
Can you help me to learn more?
(Other definitions for wring that I've seen before include "Twist and compress" , "Squeeze moisture (from)" , "Squeeze liquid from" , "Extort; wrest" , "Squeeze water out of" .)