Lay claim to occupy no French island with lake (15)
I believe the answer is:
nonprofessional
'lay' is the definition.
(synonyms)
'claim to occupy no french island with lake' is the wordplay.
I cannot really see how this works, but
'claim' could be 'profess' (professing is a kind of claiming) and 'profess' is located in the answer.
'no' could be 'non' (I've seen this in other clues) and 'non' is located in the answer.
'island' could be 'iona' (Scottish island) and 'iona' is found in the answer.
'lake' could be 'l' (geographical abbreviation) and 'l' is found within the answer.
This accounts for all the letters.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?