Given food by a fatheaded fellow (3)
I believe the answer is:
fed
'given food' is the definition.
(I've seen this in other clues)
'by a fatheaded fellow' is the wordplay.
'by' says to put letters next to each other.
'a fatheaded' becomes 'f' (this might be a standard abbreviation which I don't know about).
'fellow' becomes 'ed' (short for Edward).
'f' put next to 'ed' is 'FED'.
Can you help me to learn more?
(Other definitions for fed that I've seen before include "Nourished" , "Banking authority" , "US agent" , "Gave food to (someone)" , "Provided food for" .)