A volatility strategy (volatility trade) which combines futures and options and is constructed by buying a call option (long call) and simultaneously selling the underlying (e.g. short stock) so as the overall position delta is netted to zero.

In a nutshell, from the buy perspective:

Call volatility trade = long call + short underlying

That is:

Buy 1 call

Sell 1 underlying

Net delta = zero (or close to zero)

This results in a position which depends on the volatility of the underlying.