Country with wizard on back of merchandise has invigorating air (5)
I believe the answer is:
ozone
'invigorating air' is the definition.
(I've seen this before)
'country with wizard on back of merchandise' is the wordplay.
'country with wizard' becomes 'oz' (as in The Wizard of Oz).
'back of' indicates one should take the final letters.
The last letter of 'merchandise' is 'e'.
'oz'+'on'+'e'='OZONE'
'has' acts as a link.
(Other definitions for ozone that I've seen before include "Sea air; bleaching agent" , "Allotrope of oxygen" , "Invigorating air of the seaside" , "Colourless gas soluble in alkalis and cold water" , "Protection" .)