Hard base pilot's exploited as landing pad (8)

I haven't cracked this one yet — but the brilliant team at Fifteensquared have:

Hard base pilot’s exploited as landing pad H (=hard, as in HB pencil ) + E (=base, in mathematics) + *(PILOT’S); “exploited” is anagram indicator; Chambers lists a helistop as a landing-place for a helicopter, while Google reveals that, in the US, a helispot is a designated location near the site of a fire when firefighters’ helicopters can land!