Furnish a yak with fodder (3)
I believe the answer is:
hay
'fodder' is the definition.
(hay is a kind of fodder)
'furnish a yak with' is the wordplay.
'with' says the answer is hidden in the clue.
'HAY' is hidden in the letters of 'furnish a yak'.
(Other definitions for hay that I've seen before include "Meadow crop" , "Make . . . while the sun shines" , "Forage" , "Wye book town" , "Dried mown grass" .)