Breadwinners' hidden secret (5)
I believe the answer is:
inner
'secret' is the definition.
(thesaurus)
'breadwinners' hidden' is the wordplay.
'hidden' indicates the answer is hidden within the clue.
'INNER' is hidden in the letters of 'breadwinners'.
(Other definitions for inner that I've seen before include "Relating to the soul, mind or spirit" , "closer than magpie" , "Inside; next to the bull (archery)" , "Private, not expressed" , "Hidden" .)