Rash, heartless and hollow (6)
I believe the answer is:
recess
'hollow' is the definition.
(thesaurus)
'rash heartless' is the wordplay.
'rash' becomes 'reckless' ('reckless' can be a synonym of 'rash').
'heartless' says to hollow out the word (remove centre letters).
'reckless' with its centre removed is 'RECESS'.
'and' is the link.
(Other definitions for recess that I've seen before include "Niche, alcove" , "Enclosure set back or indented" , "Vacation's needed" , "Temporary cessation from business" , "Small set-back space" .)