Rest for swimmer crossing inside of area? (8)
I believe the answer is:
breather
'rest' is the definition.
(breather is a kind of rest)
'swimmer crossing inside of area?' is the wordplay.
'swimmer' becomes 'bather' ('bather' can be a synonym of 'swimmer'**).
'crossing' means one lot of letters goes inside another.
'inside of' says to take the centre.
The middle letters of 'area' are 're'.
'bather' enclosing 're' is 'BREATHER'.
'for' acts as a link.
(Other definitions for breather that I've seen before include "Recovery time" , "time off work" , "Short pause for rest" , "A rest - lung?" , "lung or > liver?" .)