Sea at Calais that is enthralling the writer, French writer (7)
I believe the answer is:
merimee
'writer french writer' is the definition.
I don't know anything about this answer so I cannot judge whether it can be defined by this definition.
'sea at calais that is enthralling' is the wordplay.
'sea' becomes 'mer' (I have seen 'French sea ' mean 'mer' so perhaps 'sea' could also mean 'mer').
'at calais' becomes 'me' (I can't justify this - if you can you should give a lot more credence to this answer).
'that is' becomes 'ie' (short for Latin 'id est', 'that is').
'enthralling' indicates putting letters inside.
'me' inserted within 'ie' is 'imee'.
'mer'+'imee'='MERIMEE'
'the' acts as a link.
Can you help me to learn more?