Determined at first to hold back (5)
I believe the answer is:
deter
'hold back' is the definition.
(I've seen this in another clue)
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for deter that I've seen before include "Check" , "Prevent by instilling fear" , "stop" , "'Discourage, dissuade (5)'" , "Discourage through fear of consequences" .)