They have no balls for regular returns — such madness! (7)
I believe the answer is:
eunuchs
'they have no balls' is the definition.
'regular returns such madness' is the wordplay.
'regular' means one should take alternating letters.
'madness' indicates an anagram.
The alternate letters of 'returns' are 'eun'.
'such' anagrammed gives 'uchs'.
'eun'+'uchs'='EUNUCHS'
'for' is the link.
(Other definitions for eunuchs that I've seen before include "these people are unproductive" , "They're harmless to women" , "Ineffectual people" , "Castrati" , "Harem attendants" .)