Flexible split heralded in part (5)
I believe the answer is:
lithe
'flexible' is the definition.
(thesaurus)
'split heralded in part' is the wordplay.
'in part' says the answer is hidden in the clue.
'LITHE' can be found hidden inside 'split heralded'.
(Other definitions for lithe that I've seen before include "Lissome, supple" , "Physically supple, agile" , "Physically flexible or supple" , "quick to move" , "Don -, opera by Verdi" .)