Composer was relaxed before, that is (5)
I believe the answer is:
satie
'composer' is the definition.
(French composer Erik Satie)
'relaxed before that is' is the wordplay.
'relaxed' becomes 'sat' (sitting is a type of relaxing).
'before' is a charade indicator (letters next to each other).
'that is' becomes 'ie' (abbreviation for id est, 'that is' in Latin).
'sat'+'ie'='SATIE'
'was' is the link.
(Other definitions for satie that I've seen before include "French composer (Trois Gymnopedies)" , "French composer of the Gymnopedies, d. 1925" , "creative Frenchman" , "posed by yours truly close to stage" , "Erik -, nineteenth to twentieth century French composer" .)