All so relaxed before start of major ski race (6)
I believe the answer is:
slalom
'ski race' is the definition.
(slalom is a kind of ski race)
'all so relaxed before start of major' is the wordplay.
'relaxed' indicates an anagram.
'before' says to put letters next to each other.
'start of' suggests taking the first letters.
The first letter of 'major' is 'm'.
'all'+'so'='allso'
'allso' is an anagram of 'slalo'.
'slalo'+'m'='SLALOM'
(Other definitions for slalom that I've seen before include "Downhill ski event" , "Type of ski race" , "Ski race down zig-zag course" , "Winding ski-run" , "Downhill ski-race over a winding course" .)