Swear after hounds get early start (5)
I believe the answer is:
curse
'swear' is the definition.
(I know that swear can be written as curse)
'hounds get early start' is the wordplay.
'hounds' becomes 'cure' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'get' is an insertion indicator.
'early' indicates taking the first letters (I've seen 'earliest of' mean this).
The first letter of 'start' is 's'.
'cure' going around 's' is 'CURSE'.
'after' acts as a link.
Can you help me to learn more?
(Other definitions for curse that I've seen before include "Trouble" , "Excommunication" , "Wish harm on" , "Malediction or expletive" , "Profane or obscene expression" .)