Oddly bold, one politician in balloon (5)
I believe the answer is:
blimp
'balloon' is the definition.
(thesaurus)
'oddly bold one politician' is the wordplay.
'oddly' means one should take alternating letters.
'one politician' becomes 'imp' (I've seen this in other clues).
The alternate letters of 'bold' are 'bl'.
'bl'+'imp'='BLIMP'
'in' is the link.
(Other definitions for blimp that I've seen before include "Small nonrigid airship" , "Airship - barrage balloon" , "returns one pound to provost" , "Elderly pompous reactionary person" , "David Low's cartoon colonel - airship used for publicity" .)