Make a ship unfit to carry out an attack (6)
I believe the answer is:
assail
'an attack' is the definition.
(I've seen this before)
'make a ship unfit to carry out' is the wordplay.
I cannot quite understand how this works, but
'a' is found in the answer.
'ship' could be 'ss' and 'ss' is found in the answer.
The remaining letters 'ail' is a valid word which might be clued in a way I don't understand.
This may be the basis of clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for assail that I've seen before include "Aggressively attack" , "Make violent attack on" , "Trouble" , "Go for" , "Molest or harass" .)