Eatery served up rarest tuna (10)
I believe the answer is:
restaurant
'eatery' is the definition.
(I've seen this before)
'up rarest tuna' is the wordplay.
'up' indicates an anagram.
'rarest'+'tuna'='raresttuna'
'raresttuna' with letters rearranged gives 'RESTAURANT'.
'served' acts as a link.
(Other definitions for restaurant that I've seen before include "Eatery" , "Eating place" , "table here?" .)