Ties last of livestock on board (7)
I believe the answer is:
kinship
'board' is the definition.
Although both the answer and definition are singular nouns, I cannot see how one could define the other.
'ties last of livestock on' is the wordplay.
'ties' becomes 'inship' (I am not sure about this - if you are sure you should believe this answer much more).
'last of' suggests the final letters.
'on' means one lot of letters go next to another.
The final letter of 'livestock' is 'k'.
'inship' put after 'k' is 'KINSHIP'.
Can you help me to learn more?
(Other definitions for kinship that I've seen before include "Having relations with" , "A sharing of characteristics" , "Close connection marked by interests, similarity in nature, or character" , "Blood tie" , "Blood relationship" .)