This protected by Asdic on voyage? (6)
I believe the answer is:
convoy
'this' is the definition.
The definition suggests a singular noun which matches the answer.
'protected by asdic on voyage?' is the wordplay.
'protected by' says the answer is hidden in the clue.
'CONVOY' is hidden within 'asdic on voyage'.
Can you help me to learn more?
(Other definitions for convoy that I've seen before include "Escort in transit" , "Protective escort" , "Group of vehicles moving together" , "Vehicle procession" , "Group of ships travelling together" .)