Briefly cavorting in sun at hotspot (2,1,8)
I believe the answer is:
in a nutshell
'briefly' is the definition.
(synonyms)
'cavorting in sun at hotspot' is the wordplay.
'cavorting' indicates anagramming the letters.
'hotspot' becomes 'hell' (a hot or fiery place).
'in'+'sun'+'at'='insunat'
'insunat' anagrammed gives 'inanuts'.
'inanuts'+'hell'='IN A NUTSHELL'
(Other definitions for in a nutshell that I've seen before include "Briefly, concisely" , "Something hard to crack here" , "Succinctly" , "where you'd find best part of Brazil" , "To cut a long story short" .)