Revolutionary trial keeping five in box (2,3)
I believe the answer is:
tv set
'box' is the definition.
(the box can informally mean television)
'revolutionary trial keeping five' is the wordplay.
'revolutionary' shows that the letters should be reversed in order.
'trial' becomes 'test' (synonyms).
'keeping' indicates putting letters inside.
'five' becomes 'V' (roman numeral).
'test' placed around 'v' is 'tesvt'.
'tesvt' in reverse letter order is 'TV SET'.
'in' acts as a link.
(Other definitions for tv set that I've seen before include "Goggle-box" , "'Goggle box (2,3)'" .)