leather

put on | remove, take off

in (a) ~
a horse in harness

child | safety | climbing, parachute

have on, wear | do up, fasten
She fastened the safety harness tightly round her waist before starting the descent.

undo, unfasten

in a/the ~
Another man in a harness was being lowered from the helicopter.

effectively, successfully | fully

attempt to, seek to, try to
attempting to harness the power of the sun

manage to

for
How can this energy be harnessed effectively for the good of humankind?