Most picturesque island crossed by soldier partaking in mission (9)
I believe the answer is:
quaintest
'most picturesque' is the definition.
Both the answer and definition are superlative adjectives. Perhaps there's a link between them I don't understand?
'island crossed by soldier partaking in mission' is the wordplay.
I cannot really understand how this works, but
'island' could be 'i' (geographical abbreviation) and 'i' is found within the answer.
'soldier' could be 'ant' (soldier is a type of ant) and 'ant' is found within the remaining letters.
'mission' could be 'quest' (a quest is a mission or search) and 'quest' is found within the leftover letters.
No letters remain.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Another definition for quaintest that I've seen is " Most unusual".)