Cavorting in sauna there will give you an attack of nerves (12)
I believe the answer is:
neurasthenia
'an attack of nerves' is the definition.
(historical term for a nervous condition)
'cavorting in sauna there' is the wordplay.
'cavorting' is an anagram indicator.
'in'+'sauna'+'there'='insaunathere'
'insaunathere' anagrammed gives 'NEURASTHENIA'.
'will give you' acts as a link.
(Other definitions for neurasthenia that I've seen before include "stress condition" , "psychological disorder?" , "Nervous debility" , "Nervous condition" .)