Prolonged muscle contraction set tuna swimming (7)
I believe the answer is:
tetanus
'prolonged muscle contraction' is the definition.
Although both the answer and definition are singular nouns, I can't understand how they can define each other.
'set tuna swimming' is the wordplay.
'swimming' is an anagram indicator.
'set'+'tuna'='settuna'
'settuna' is an anagram of 'TETANUS'.
Can you help me to learn more?
(Other definitions for tetanus that I've seen before include "infectious disease" , "Locker" , "Disease causing muscular spasms" , "Attunes to disease from dog-bite" , "Attunes (anag) - muscular illness" .)