In two minds over a party storm (7)
I believe the answer is:
tornado
'storm' is the definition.
(type of weather)
'in two minds over a party' is the wordplay.
'in two minds' becomes 'torn' (I've seen this before).
'over' means one lot of letters go next to another.
'party' becomes 'do' (do is a kind of party).
'torn'+'a'+'do'='TORNADO'
(Other definitions for tornado that I've seen before include "Destructive windstorm" , "Strong wind" , "Funnelling wind" , "Whirling storm" , "Type of cyclone" .)