A bit of loin, regularly wanting garlic sauce (5)
I believe the answer is:
aioli
'garlic sauce' is the definition.
(synonyms)
'a bit of loin regularly' is the wordplay.
'regularly' means one should take alternating letters (regularly take one letter, leave next etc.).
'bit'+'of'+'loin'='bitofloin'
The alternate letters of 'bitofloin' are 'ioli'.
'a'+'ioli'='AIOLI'
'wanting' is the link.
(Other definitions for aioli that I've seen before include "garlic dip" , "A lamb joint; driven clouds" , "Garlic 9" , "Sort of mayonnaise" , "Garlic mayo" .)