Old statesman to boast briefly, suppressing reserve (6)
I believe the answer is:
cicero
'old statesman' is the definition.
(Roman politician)
'boast briefly suppressing reserve' is the wordplay.
'boast' becomes 'crow' (crow is a kind of boast).
'briefly' means to remove the last letter.
'suppressing' is an insertion indicator.
'reserve' becomes 'ice' (I've seen this before).
'crow' with its last letter removed is 'cro'.
'cro' enclosing 'ice' is 'CICERO'.
'to' acts as a link.
(Other definitions for cicero that I've seen before include "Marcus Tullius -, Roman consul, orator and writer" , "Roman stylist, orator" , "Roman lawyer" , "Old politician" , "accomplished orator" .)