Weapon held in parliament, first of all, for Westminster official? (4)

22A — Weapon held in parliament, first of all, for Westminster official? (4) — WHIP

• Definition
  Definition found: 'Westminster official?' — The definition is the last two words — a party's parliamentary enforcer. Show hint
• Indicator
  Indicator found: 'first of all,' Show hint
• Operation
  'first of all,' signals a letter_selection operation
• Fodder
  Fodder: 'Weapon held in parliament,'
• Assembly
  WHIP = WHIP

Try this clue in the trainer →