Promises empty pill has advantages (7)
I believe the answer is:
pledges
'promises' is the definition.
(pledging is a kind of promising)
'empty pill has advantages' is the wordplay.
'empty' means to remove the middle letters.
'has' means one lot of letters go next to another.
'advantages' becomes 'edges' (edge is a kind of advantage).
'pill' with its middle removed is 'pl'.
'pl'+'edges'='PLEDGES'
(Other definitions for pledges that I've seen before include "Vows" , "Promises" , "Loyal toasts" .)