Complaint from motoring organisation about street followed by Her Majesty (6)
I believe the answer is:
asthma
'complaint' is the definition.
(asthma is a kind of disease)
'motoring organisation about street followed by her majesty' is the wordplay.
'motoring organisation' becomes 'aa'.
'about' is an insertion indicator.
'street' becomes 'st'.
'followed by' means one lot of letters go next to another.
'her majesty' becomes 'hm'.
'st'+'hm'='sthm'
'aa' going around 'sthm' is 'ASTHMA'.
'from' acts as a link.
(Other definitions for asthma that I've seen before include "Lung condition" , "Respiratory condition" , "Physical disorder" , "Strange that Mat has difficulty breathing" , "Mat has a respiratory disorder" .)