Pound and a half they nick (5)
I believe the answer is:
throb
'pound' is the definition.
(I know that pound is a is a kind of of throb)
'a half they nick' is the wordplay.
'a half' means to take half the letters.
'nick' becomes 'rob' (both can mean to steal).
'they' cut in half is 'th'.
'th'+'rob'='THROB'
'and' is the link.
(Other definitions for throb that I've seen before include "Sound of engines" , "Palpitate, quiver (with emotion)" , "Pulse" , "beat repeatedly" , "Martin -; Kingsley -" .)