It enabled Jason to be nautical (4)
I believe the answer is:
argo
'it enabled jason' is the definition.
The definition suggests a singular noun which matches the answer.
'be nautical' is the wordplay.
I cannot quite understand how this works, but
'be' could be 'go' (going is a kind of being) and 'go' is found within the answer.
The remaining letters 'ar' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...
'to' acts as a link.
Can you help me to learn more?
(Other definitions for argo that I've seen before include "Fabulous ship" , "Stars once recognised in the south" , "Ship involved in the quest for the Golden Fleece" , "Constellation; ship" , "Ship in which Jason searched for the Golden Fleece" .)