Rent trouble? That's a blow! (7)
I believe the answer is:
tornado
'a blow' is the definition.
(I have seen 'Dreadful blow' mean 'tornado' so perhaps 'blow' could also mean 'tornado')
'rent trouble?' is the wordplay.
'rent' becomes 'torn' ('torn' can be a synonym of 'rent').
'trouble?' becomes 'ado' (I've seen this before).
'torn'+'ado'='TORNADO'
'that's' is the link.
(Other definitions for tornado that I've seen before include "Violent twister" , "Destructive windstorm" , "Rapidly whirling column of air" , "Cyclone, twister" , "Major storm" .)