Extremely irate after politician collecting silver becomes hoarder (6)
I believe the answer is:
magpie
'hoarder' is the definition.
(synonyms)
'extremely irate after politician collecting silver' is the wordplay.
'extremely' suggests removing the centre (only the extremes of the word are used).
'after' means one lot of letters go next to another.
'politician' becomes 'MP' (Member of Parliament).
'collecting' is an insertion indicator.
'silver' becomes 'Ag' (Ag is the chemical symbol for silver).
'irate' with its centre taken out is 'ie'.
'mp' enclosing 'ag' is 'magp'.
'ie' after 'magp' is 'MAGPIE'.
'becomes' acts as a link.
(Other definitions for magpie that I've seen before include "Black and white bird, may be thieving" , "Black and white bird - a thief" , "Bird of the crow family" , "One on target" , "Part of target" .)