Storm off set, with stopgap taking lead part (7)
I believe the answer is:
tempest
'storm off set' is the definition.
'tempest' can be an answer for 'storm' (thesaurus). I am not certain of the 'off set' bit.
'with stopgap taking lead part' is the wordplay.
'with' says to put letters next to each other.
'stopgap' becomes 'temp'.
'taking lead part' becomes 'est' (I am not sure about this - if you are sure you should believe this answer much more).
'temp' put next to 'est' is 'TEMPEST'.
(Other definitions for tempest that I've seen before include "Bad weather" , "A violent storm like Shakespeare's" , "Violent wind storm" , "A great storm of wind and rain" , "Furore" .)