Poorly, for example? Not half! (3,3)
I believe the answer is:
ill say
'not half' is the definition.
(both can be used to express agreement)
'poorly for example?' is the wordplay.
'poorly' becomes 'ill' (synonyms).
'for example?' becomes 'say' ('say' can be used to introduce an example).
'ill'+'say'='ILL SAY'
(Other definitions for ill say that I've seen before include "Injuries" , "Indubitably" , "You bet" , "Absolutely!" , "Rather!" .)