Cricket side in wizard place initially enjoying bracing air (5)
I believe the answer is:
ozone
'bracing air' is the definition.
(I've seen this before)
'cricket side in wizard place initially enjoying' is the wordplay.
'cricket side' becomes 'on' (cricket term, on or leg side).
'in' means one lot of letters goes inside another.
'wizard place' becomes 'oz'.
'initially' indicates taking the first letters.
The initial letter of 'enjoying' is 'e'.
'oz'+'e'='oze'
'on' inserted into 'oze' is 'OZONE'.
(Other definitions for ozone that I've seen before include "It's said to brace" , "bracing atmosphere" , "Gas that screens ultraviolet radiation" , "Bracing seaside air" , "Layer that protects against ultraviolet rays" .)