Puzzle ZQOI 

Workings

Hint
The question contains the answer.

Answer
FOOT.

Take the first letter of the second word
   + the first letter of the first word
   + the second letter of the first word
   + the last letter of the second word.

Double-Checking
23-- [1234] 1--4
EA-- [HEAD] H--D
OO-- [FOOT] F--T