Venice exposed with rising sea coming in across the region (7)
I believe the answer is:
endemic
'in across the region' is the definition.
I can't judge whether this defines the answer.
'venice exposed with rising sea' is the wordplay.
'exposed' indicates the central letters (the inside of the word is exposed).
'with' means one lot of letters goes inside another.
'rising' says the letters should be written in reverse (in a down clue, letters go up).
'sea' becomes 'med' (short for Mediterranean).
The central letters of 'venice' are 'enic'.
'med' reversed gives 'dem'.
'enic' enclosing 'dem' is 'ENDEMIC'.
'coming' is the link.
Can you help me to learn more?
(Other definitions for endemic that I've seen before include "restricted to a particular area" , "Localised" , "Belonging to a particular area" , "Restricted to a certain area" , "Confined to a particular area" .)