Cooks pig's heart inside for leaders (6)
I believe the answer is:
chiefs
'for leaders' is the definition.
(chief is a kind of leader)
'cooks pig's heart' is the wordplay.
'cooks' becomes 'chefs' (chef is a kind of cook).
'pig's' becomes 'i' (I can't justify this - if you can you should give a lot more credence to this answer).
'heart' means one lot of letters goes inside another.
'chefs' going around 'i' is 'CHIEFS'.
'inside' is the link.
Can you help me to learn more?
(Other definitions for chiefs that I've seen before include "Leaders, bigwigs" , "Leaders, heads" , "Bosses, gaffers" , "Leaders, bosses" , "Heads top dogs" .)