Expression of surprise about old politician’s pizzazz (5)
I believe the answer is:
oomph
'pizzazz' is the definition.
(I know that pizzazz can be written as oomph)
'expression of surprise about old politician's' is the wordplay.
'expression of surprise' becomes 'oh'.
'about' indicates putting letters inside.
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'politician' becomes 'MP' (Member of Parliament).
'o'+'mp'='omp'
'oh' enclosing 'omp' is 'OOMPH'.
(Other definitions for oomph that I've seen before include "drive" , "vital quality" , "Vitality, zing" , "Go" , "Enthusiasm - vigour - sex appeal" .)