American brought up his poorly prepared food (5)
I believe the answer is:
sushi
'prepared food' is the definition.
'sushi' can be an answer for 'food' (sushi is a kind of food). I am not certain of the 'prepared' bit.
'american brought up his poorly' is the wordplay.
'american' becomes 'US' (abbreviation for United States).
'brought up' is a reversal indicator (in a down clue, letters go up).
'poorly' indicates an anagram (a poor spelling).
'us' back-to-front is 'su'.
'his' with letters rearranged gives 'shi'.
'su'+'shi'='SUSHI'
Can you help me to learn more?
(Other definitions for sushi that I've seen before include "cold food" , "oriental dish" , "Exotic food" , "Japanese cuisine" , "Japanese rice and raw fish dish" .)