Clue: A politician catching balls initially is clumsy with both hands (12)
Answer: AMBISINISTER
Explanation: Definition: clumsy with both hands
An envelope ('catching') of B ('**B**alls initially') plus 'is' in 'a' plus MINISTER ('politician'). A new one for me, but obvious: if "ambidextrous" is equally skillful with both hands, AMBISINISTER is equally clumsy.