Decides former tennis player keeps dry (7)
I believe the answer is:
settles
'decides' is the definition.
('settle' can be a synonym of 'decide')
'former tennis player keeps dry' is the wordplay.
'former tennis player' becomes 'Seles' (Monica Seles).
'keeps' indicates putting letters inside (inserted letters are kept inside).
'dry' becomes 'tt' (short for teetotal - no alcohol).
'seles' going around 'tt' is 'SETTLES'.
(Other definitions for settles that I've seen before include "Becomes established in a place" , "Resolves" , "furniture" , "Pays the bill" , "Comes to rest" .)