Spot youth at intervals enthralled by French resort (6)
I believe the answer is:
notice
'spot' is the definition.
(I've seen this in another clue)
'youth at intervals enthralled by french resort' is the wordplay.
'at intervals' indicates alternate letters (letters are taken at regular intervals).
'enthralled' is an insertion indicator.
'by french resort' becomes 'nice' (I can't justify this - if you can you should believe this answer much more).
The alternating letters of 'youth' are 'ot'.
'ot' going within 'nice' is 'NOTICE'.
Can you help me to learn more?
(Other definitions for notice that I've seen before include "Observe - about to resign?" , "Become aware of; review" , "Announcement with information about a future event" , "See; advert" , "Detect" .)