Aim of busy environmentalist, saving marvels at sea (9)
I believe the answer is:
intention
'aim' is the definition.
(I know that aim can be written as intention)
'environmentalist saving marvels at sea' is the wordplay.
'saving' is a deletion indicator (saving can mean except).
'at sea' is an anagram indicator.
'environmentalist' with 'marvels' removed is 'nionentit'.
'nionentit' anagrammed gives 'INTENTION'.
'of busy' is the link.
I am not very happy about this link. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for intention that I've seen before include "Aim, plan" , "Design" , "Aim, purpose" , "Plan, purpose" , "goal" .)