Herbal tea or teas in mess (6)
I believe the answer is:
tisane
'herbal tea' is the definition.
(tisane is a kind of herbal tea)
'teas in mess' is the wordplay.
'mess' is an anagram indicator.
'teas'+'in'='teasin'
'teasin' is an anagram of 'TISANE'.
'or' is the link.
(Other definitions for tisane that I've seen before include "Herbal tea drink" , "brew" , "Herb tea" , "Herbal infusion" , "relaxing drink" .)