Heartless family to upset toads (4)
I believe the answer is:
knot
'heartless family to upset toads' is the definition.
I can't tell whether this defines the answer.
'heartless family to upset' is the wordplay.
'heartless' says to hollow out the word (remove centre letters).
'family' becomes 'kin' (synonyms).
'upset' shows that the letters should be reversed in order.
'kin' with its middle removed is 'kn'.
'to' in reverse letter order is 'ot'.
'kn'+'ot'='KNOT'
Can you help me to learn more?
(Other definitions for knot that I've seen before include "Tie cord - lump in timber" , "Hard round cross-grained piece in wood" , "Ligature" , "Hard mass in tree trunk at branch joint" , "Difficult problem" .)