Submit box containing diamonds (5)
I believe the answer is:
lodge
'submit' is the definition.
(thesaurus)
'box containing diamonds' is the wordplay.
'box' becomes 'loge' ('loge' can be a synonym of 'box'**).
'containing' indicates putting letters inside.
'diamonds' becomes 'd' (abbreviation in bridge say).
'loge' going around 'd' is 'LODGE'.
(Other definitions for lodge that I've seen before include "Register" , "Cottage at the entrance to the grounds of a big house" , "See 2" , "Cabin for seasonal activity - become embedded" , "Comic novelist" .)