Sort out a maths problem (6)
I believe the answer is:
asthma
'problem' is the definition.
(I have seen 'Respiratory problem ' mean 'asthma' so perhaps 'problem' could also mean 'asthma')
'sort out a maths' is the wordplay.
'sort out' indicates an anagram.
'a'+'maths'='amaths'
'amaths' anagrammed gives 'ASTHMA'.
(Other definitions for asthma that I've seen before include "Cause of breathing difficulty" , "Lung condition" , "Distressing ailment affecting breathing" , "Physical disorder" , "Mat has a respiratory disorder" .)