Rambert's head stopping basic support for dancers (5)
I believe the answer is:
barre
'support for dancers' is the definition.
(type of bar used in ballet)
'rambert's head stopping basic' is the wordplay.
'head' suggests taking the first letters.
'stopping' means one lot of letters goes inside another (stopping can mean blocking a gap).
'basic' becomes 'bare'.
The first letter of 'rambert' is 'r'.
'r' inserted inside 'bare' is 'BARRE'.
(Other definitions for barre that I've seen before include "Ballet dancers' support" , "Where dancer goes for practice" , "Capo" , "At which a ballet dancer exercises" , "Ballet exercise support" .)