Fail to put on a stone, after sending up special meals (5)
I believe the answer is:
diets
'special meals' is the definition.
'fail to put on a stone after sending up' is the wordplay.
'fail' becomes 'die' ('die' can be a synonym of 'fail').
'to put on' says to put letters next to each other.
'a stone' becomes 'st'.
'after sending up' shows that the letters should be reversed in order (in a down clue, letters go up).
'st' in reverse letter order is 'ts'.
'die'+'ts'='DIETS'
(Other definitions for diets that I've seen before include "Commons" , "Disciplined eating regimes" , "causing stones to vanish" , "Regimens" , "Legislative assemblies" .)