Exploits the last post in America (4)
I believe the answer is:
taps
'exploits the last post in america' is the definition.
'taps' can be an answer for 'exploits' (to tap is to exploit or make use of something). I am unsure of the 'the last post in america' bit.
This is the entire clue.
Can you help me to learn more?
(Other definitions for taps that I've seen before include "Exploits" , "Thread cutters' strikes" , "They're faucets in America" , "Strikes lightly; eavesdropping devices" , "Uses listening devices" .)