Gaseous element identified by academy teacher (5)
I believe the answer is:
radon
'gaseous element' is the definition.
(I've seen this in another clue)
'academy teacher' is the wordplay.
'academy' becomes 'RA' (Royal Academy of Arts).
'teacher' becomes 'don' (don can mean an academic - especially at Oxbridge).
'ra'+'don'='RADON'
'identified by' acts as a link.
(Other definitions for radon that I've seen before include "Element, symbol Rn" , "A radioactive gas, symbol Rn" , "Noble gas, Rn" , "Natural gas considered a hazard to health" , "hazardous substance" .)