In truth, a yellowish type of fodder (3)
I believe the answer is:
hay
'type of fodder' is the definition.
'in truth a yellowish' is the wordplay.
'in' indicates a hidden word.
'HAY' is hidden within 'truth a yellowish'.
(Other definitions for hay that I've seen before include "It is to be made while the sun shines" , "Straw" , "Dried mown grass" , "Make . . . while the sun shines" , "Wye book town" .)