Cheeky minx undressed by stretch of water (8)
I believe the answer is:
insolent
'cheeky' is the definition.
(I've seen this before)
'minx undressed by stretch of water' is the wordplay.
'undressed' indicates the central letters (the word removes the letters which clothe it).
'by' means one lot of letters go next to another.
'stretch of water' becomes 'solent' (I've seen this before).
The middle of 'minx' is 'in'.
'in'+'solent'='INSOLENT'
(Other definitions for insolent that I've seen before include "Bold" , "Lippy" , "Rudely disrespectful" , "Rude, showing lack of respect" , "Brash" .)