Life in Spa is extremely routine (6)
I believe the answer is:
breath
'life' is the definition.
(I've seen this in another clue)
'in spa is extremely routine' is the wordplay.
'in' is an insertion indicator.
'spa' becomes 'bath'.
'is extremely' says to hollow out the word (remove centre letters) (only the extremes of the word are used).
'routine' with its middle taken out is 're'.
'bath' enclosing 're' is 'BREATH'.
(Other definitions for breath that I've seen before include "Bertha (anag.)" , "Bather (anag.)" , "Air in an out of the lungs" , "Intake of air" , "from which inspiration may be drawn" .)