Huge and cerebral, performing with hesitation inside (10)
I believe the answer is:
monumental
'huge' is the definition.
(thesaurus)
'cerebral performing with hesitation inside' is the wordplay.
'cerebral' becomes 'mental' (I've seen this before).
'performing' becomes 'on' (as in being on stage).
'with' means one lot of letters go next to another.
'hesitation' becomes 'um' (sound made when hesitating).
'inside' means one lot of letters goes inside another.
'on'+'um'='onum'
'mental' enclosing 'onum' is 'MONUMENTAL'.
'and' acts as a link.
(Other definitions for monumental that I've seen before include "Great in importance" , "Large and important" , "Enormous" , "Massive and lasting" , "Stupendous" .)