Without source, fop twice claiming party's leader is BBC puppet (4,5)

'bbc puppet' is the definition.
I know nothing about this answer so I cannot judge whether this works.

'without source fop twice claiming party's leader' is the wordplay.
'without source' means to remove the first letter.
'fop' becomes 'dandy' (synonyms).
'twice' shows that letters should be duplicated.
'claiming' means one lot of letters goes inside another.
'party's leader' becomes 'p' (I can't justify this - if you can you should believe this answer much more).
'dandy' with its initial letter removed is 'andy'.
'andy' doubled is 'andyandy'.
'andyandy' enclosing 'p' is 'ANDY-PANDY'.

'is' is the link.

Can you help me to learn more?