On short rations as commanded by Iron Duke (8)
I believe the answer is:
underfed
'on' is the definition.
Both the answer and definition are adjectives. Perhaps there's an association between them I don't understand?
'short rations as commanded by iron duke' is the wordplay.
'short' says to take the initial letters.
'as commanded' becomes 'unde' (I can't justify this - if you can you should give a lot more credence to this answer).
'by' is a charade indicator (letters next to each other).
'iron' becomes 'Fe' (chemical symbol for iron).
'duke' becomes 'd' (abbreviation).
The initial letter of 'rations' is 'r'.
'r' put after 'unde' is 'under'.
'under'+'fe'+'d'='UNDERFED'
Can you help me to learn more?
(Other definitions for underfed that I've seen before include "in a starved condition" , "Malnourished" , "Too thin?" , "Not having enough to eat" , "deprived of basic need" .)