It sailed in far gone days (4)
I believe the answer is:
argo
'it sailed' is the definition.
The definition suggests a singular noun which matches the answer.
'in far gone days' is the wordplay.
'in' says the answer is hidden in the clue.
'ARGO' is hidden within 'far gone days'.
Can you help me to learn more?
(Other definitions for argo that I've seen before include "Old boat" , "Stars once recognised in the south" , "Mythological ship" , "Old sailing vessel" , "Agro about the constellation" .)