A politician was untruthful about condition being strengthened (9)
I believe the answer is:
amplified
'being strengthened' is the definition.
(thesaurus)
'a politician was untruthful about condition' is the wordplay.
'politician' becomes 'mp'.
'was untruthful' becomes 'lied' (I've seen this before).
'about' indicates putting letters inside.
'condition' becomes 'if' (I've seen this in other clues**).
'lied' going around 'if' is 'lified'.
'a'+'mp'+'lified'='AMPLIFIED'
(Other definitions for amplified that I've seen before include "increased in loudness" , "Made louder" , "Intensified" .)