Bit from a magnet broken by father (8)
I believe the answer is:
fragment
'bit' is the definition.
(I've seen this before)
'a magnet broken by father' is the wordplay.
'broken' is an anagram indicator.
'by' means one lot of letters go next to another.
'father' becomes 'fr' (abbreviation as in a priest's title).
'magnet' with letters rearranged gives 'agment'.
'agment' after 'fr' is 'FRAGMENT'.
'from' is the link.
(Other definitions for fragment that I've seen before include "Shard" , "Come to pieces" , "Small portion" , "Incomplete part" , "Piece broken off something else" .)