Old politician stops dog finding fluffy ball (6)
I believe the answer is:
pompom
'fluffy ball' is the definition.
(a pompom is a decorative fluffy ball)
'old politician stops dog' is the wordplay.
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'politician' becomes 'MP' (Member of Parliament).
'stops' means one lot of letters goes inside another.
'dog' becomes 'pom' (short for Pomeranian).
'o'+'mp'='omp'
'omp' inserted into 'pom' is 'POMPOM'.
'finding' is the link.
(Other definitions for pompom that I've seen before include "Fluffy ball - type of gun" , "Anti-aircraft weapon" , "Hat ornament" , "Woolly decoration" , "Decorative ball of tufted wool" .)