Mistake about Henry taking on storm (7)
I believe the answer is:
typhoon
'storm' is the definition.
(typhoon is a kind of storm)
'mistake about henry taking on' is the wordplay.
'mistake' becomes 'typo' (typographical error).
'about' means one lot of letters goes inside another.
'henry' becomes 'H' (symbol for the unit of electrical inductance).
'taking' is a charade indicator (letters next to each other).
'typo' placed around 'h' is 'typho'.
'typho'+'on'='TYPHOON'
(Other definitions for typhoon that I've seen before include "Tropical cyclone" , "Violent cyclonic storm" , "Indian Ocean tropical storm" , "Pacific tropical storm" , "Storm, cyclone" .)