Grain plant's former boss in Philippines keeping head down (6)
I believe the answer is:
quinoa
'head down' is the definition.
The definition suggests a singular noun which matches the answer.
'grain plant's former boss in philippines' is the wordplay.
I cannot quite understand how this works, but
'in' is found in the answer.
This may be the basis of clue (or it may be nonsense).
'keeping' is the link.
Can you help me to learn more?
(Other definitions for quinoa that I've seen before include "South American grain" , "Grain-like crop from South America" , "Vegan food" .)