Garlic mayonnaise: superior colloid used regularly (5)
I believe the answer is:
aioli
'garlic mayonnaise' is the definition.
(aioli is a condiment)
'superior colloid used regularly' is the wordplay.
'superior' becomes 'ai' (I can't explain this - if you can you should give a lot more credence to this answer).
'used regularly' means one should take alternating letters.
The alternate letters of 'colloid' are 'oli'.
'ai'+'oli'='AIOLI'
Can you help me to learn more?
(Other definitions for aioli that I've seen before include "Garlic 9" , "Mayonnaise with garlic" , "Garnish" , "Garlicky mayonnaise" , "mayonniase" .)