Assemble before empty court (5)
I believe the answer is:
erect
'assemble' is the definition.
(thesaurus)
'before empty court' is the wordplay.
'before' becomes 'ere' (usually literary).
'empty' suggests removing the centre.
'court' with its middle removed is 'ct'.
'ere'+'ct'='ERECT'
(Other definitions for erect that I've seen before include "Upright; construct" , "Build - straight up" , "Standing straight" , "Build, put up" , "Upstanding" .)