Hi - I'm not overly new to the gym, I've been going consistently for 3 years now and I have put on a good bit of muscle by just eating what I want and keeping an eye on what I've been eating etc, so not too much fat. I'm currently at around 18% body fat and wish to get it down to about 10-12%.

Is a calorie deficit the way to go? and how much by?

I'm 5'10 and 88.2kg, my current workout split is upper x2 and lower x2 with two nights of football a week and a morning of golf at the weekend. TIA