Stick had broken before (6)
I believe the answer is:
adhere
'stick' is the definition.
(synonyms)
'had broken before' is the wordplay.
'broken' is an anagram indicator.
'before' becomes 'ere' (poetic term for 'before').
'had' with letters rearranged gives 'adh'.
'adh'+'ere'='ADHERE'
(Other definitions for adhere that I've seen before include "Stick to - cement" , "Agree" , "Cling, attach" , "Stick firmly" , "secure" .)