Endless French article about relaxing (9)
I believe the answer is:
unceasing
'endless' is the definition.
(I've seen this in another clue)
'french article about relaxing' is the wordplay.
'french article' becomes 'un' (indefinite article in French).
'about' becomes 'c' (abbreviation for 'circa').
'relaxing' becomes 'easing' (eg relaxing or easing some pressure).
'un'+'c'+'easing'='UNCEASING'
(Other definitions for unceasing that I've seen before include "Continuous" , "Constant" , "Never ending" , "Not stopping" , "Endless" .)