Harsh letters reveal the end of ship (9)
I believe the answer is:
sternpost
'the end of ship' is the definition.
The definition suggests a singular noun which matches the answer.
'harsh letters' is the wordplay.
'harsh' becomes 'stern' (I've seen this before).
'letters' becomes 'post' (letters in the mail or post).
'stern'+'post'='STERNPOST'
'reveal' is the link.
Can you help me to learn more?
(Other definitions for sternpost that I've seen before include "Ship's upright to which rudder is attached" , "supporter on board" , "supporter in the main" .)