Good question to which I don't know the answer off the top of my head (normally I'm on the A46 or NCN15/48). Will try and remember to look out next time I'm down that way (once the weather is less wintry).

Rushcliffe Council do suggest it's the latter however "Rushcliffe Green Belt Review " (Part 2B, Jan 2016)

It's a new balancing pond that was made as part of the (ongoing) A453 widening works. Have updated as natural=water / water=drain. None of the construction work is yet visible on Bing so it should be treated as inaccurate along the A453 from the A52 to the M1.