Power Russian plane with hydrogen tank at the front (5)
I believe the answer is:
might
'power' is the definition.
(synonyms)
'russian plane with hydrogen tank at the front' is the wordplay.
'russian plane' becomes 'MiG' (MiG is a Russian aircraft manufacturer).
'with' means one lot of letters go next to another.
'at the front' indicates taking the first letters.
The first letters of 'hydrogen tank' is 'ht'.
'mig'+'ht'='MIGHT'
(Other definitions for might that I've seen before include "Doubtful" , "It expresses possibility" , "Powerfulness" , "Strength - could possibly" , "Great power/strength" .)