Beats half of them and steals from (6)
I believe the answer is:
throbs
'beats' is the definition.
(throb is a kind of beat)
'half of them and steals from' is the wordplay.
'half of' suggests halving the letters.
'and' is a charade indicator (letters next to each other).
'steals from' becomes 'robs' (I've seen this in another clue).
'them' with half the letters taken is 'th'.
'th'+'robs'='THROBS'
(Other definitions for throbs that I've seen before include "Beats with persistent rhythm, as heart does" , "Beats as a pulse" , "Pulsates like heart" , "Pounds" , "Pulsates, with pain perhaps" .)