Cap boss put on equipment (8)
I believe the answer is:
headgear
'cap' is the definition.
(thesaurus)
'boss put on equipment' is the wordplay.
'boss' becomes 'head' (synonyms).
'put on' says to put letters next to each other.
'equipment' becomes 'gear' (gear is a kind of equipment).
'head'+'gear'='HEADGEAR'
(Other definitions for headgear that I've seen before include "Hats, bonnets, caps etc" , "crown, say" , "Mortarboard < , especially" , "Hats, helmets etc." , "Aged hare? (anagram)" .)