Powdered seed tablets — first couple taken last — one must swallow (8)

I haven't cracked this one yet — but the brilliant team at Fifteensquared have:

[ PILLS(tablets, of medicine, say) with its 1st 2 letters ( first couple ) moved to the end( taken last ) ] contained in ( … must swallow ) ACE(one, as in the playing card, “the ace of heats”).