Gate to "The Wrestling Fields". Presumably this was a local hot spot for Cornish wrestling at some point. It also explains why the surf spot in front is known as wrestles.
The plaque on the gate reads:
"Jack Spong Aug 2002 - Loveable rogue who lived for his friends, waves and beer at wrestles"
It is a dedication to a 22 year old who drowned that year at Gwithian.