By empty hall, reference back-flipping Sporty (8)
I believe the answer is:
athletic
'sporty' is the definition.
(I've seen this in another clue)
'by empty hall reference back' is the wordplay.
'by' becomes 'at' ().
'empty' says to hollow out the word (remove centre letters).
'reference' becomes 'cite' (to cite is to mention or quote).
'back' is a reversal indicator.
'hall' with its centre taken out is 'hl'.
'cite' back-to-front is 'etic'.
'at'+'hl'+'etic'='ATHLETIC'
'flipping' acts as a link.
This may not be correct. It may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for athletic that I've seen before include "Lithe act (anag)" , "Fit and sporty" , "Muscular" , "Physically fit, strong and active" , "Good at running and jumping" .)