Respiratory disorder caught early (4)
I believe the answer is:
cold
'respiratory disorder' is the definition.
(cold is a kind of respiratory disorder)
'caught early' is the wordplay.
'caught' becomes 'c' (cricket abbreviation).
'early' becomes 'old' ('old' can be similar in meaning to 'early').
'c'+'old'='COLD'
(Other definitions for cold that I've seen before include "Mild viral infection, very common" , "Unsympathetic" , "Glacial" , "Unfriendly" , "Frigid" .)