Call wife or mistress initially making a complaint (8)
I believe the answer is:
ringworm
'a complaint' is the definition.
(ringworm is a kind of disease)
'call wife or mistress initially' is the wordplay.
'call' becomes 'ring' (synonyms).
'wife' becomes 'w'.
'initially' suggests taking the first letters.
The initial letter of 'mistress' is 'm'.
'ring'+'w'+'or'+'m'='RINGWORM'
'making' acts as a link.
(Other definitions for ringworm that I've seen before include "ailment" , "Fungal infection of the skin characterised by round patches" , "Skin disease" , "Tinea" , "Problem with skin" .)