Son getting spa treatments lies back, rests (6)
I believe the answer is:
sleeps
'rests' is the definition.
('sleep' can be a synonym of 'rest')
'son getting spa treatments lies back' is the wordplay.
'son' becomes 's' (genealogical abbreviation for son).
'getting' is a charade indicator (letters next to each other).
'spa treatments' becomes 'peels' (I've seen this in another clue).
'lies back' shows that the letters should be reversed in order (I've seen 'lying back' mean this).
'peels' in reverse letter order is 'sleep'.
's' after 'sleep' is 'SLEEPS'.
(Other definitions for sleeps that I've seen before include "Dozes" , "Takes a siesta" , "Slumbers" , "Rests in the arms of Morpheus" , "Catches some Z's" .)