Power of an aircraft at height (5)
I believe the answer is:
might
'power' is the definition.
(synonyms)
'an aircraft at height' is the wordplay.
'an aircraft' becomes 'mig' (I have seen 'Russian aircraft ' mean 'mig' so perhaps 'aircraft' could also mean 'mig').
'at' means one lot of letters go next to another.
'height' becomes 'ht' (abbreviation).
'mig'+'ht'='MIGHT'
'of' acts as a link.
(Other definitions for might that I've seen before include "Physical strength of old" , "Strength - could possibly" , "word expressing possibility" , "Force; could" , "Clout" .)