Act ends after moving melody (7)
I believe the answer is:
descant
'melody' is the definition.
(descant is a kind of melody)
'act ends after moving' is the wordplay.
'after moving' indicates anagramming the letters.
'act'+'ends'='actends'
'actends' is an anagram of 'DESCANT'.
(Other definitions for descant that I've seen before include "Independent treble line" , "Sung variation" , "Upper melody" , "Treble melody part" , "Ornamental melody added above a theme" .)