Hold I cannot break (7)
I believe the answer is:
contain
'hold' is the definition.
('contain' can be a synonym of 'hold')
'i cannot break' is the wordplay.
'break' is an anagram indicator.
'i'+'cannot'='icannot'
'icannot' with letters rearranged gives 'CONTAIN'.
(Other definitions for contain that I've seen before include "keep within bounds" , "I cannot (anag) - hold back" , "Keep the lid on" , "Enclose" , "Include - restrict" .)