Young one on farm has broken leg in deep hole (6)
I believe the answer is:
piglet
'young one on farm' is the definition.
(young pig)
'broken leg in deep hole' is the wordplay.
'broken' is an anagram indicator.
'in' is an insertion indicator.
'deep hole' becomes 'pit' (I've seen this before).
'leg' with letters rearranged gives 'gle'.
'gle' going inside 'pit' is 'PIGLET'.
'has' acts as a link.
(Other definitions for piglet that I've seen before include "One with home in Hundred Acre Wood" , "Young porker" , "Young sow or boar" , "19's little friend" , "8's friend (the timid one)" .)