Pass on tasteless empty fasts (5)
I believe the answer is:
diets
'fasts' is the definition.
(dieting is a kind of fasting)
'pass on tasteless empty' is the wordplay.
'pass' becomes 'die' (as in passing away).
'on' means one lot of letters go next to another.
'empty' suggests removing the centre.
'tasteless' with its centre removed is 'ts'.
'die'+'ts'='DIETS'
(Other definitions for diets that I've seen before include "Tides (anag.)" , "Disciplined eating regimes" , "Legislative assemblies" , "Regimens" , "causing stones to vanish" .)