Block entrance to conservatory during Cluedo unfortunately (7)

I haven't cracked this one yet — but the brilliant team at Fifteensquared have:

Block entrance to conservatory during Cluedo unfortunately C <onservatory> (“entrance to” means first letter only) in *(CLUEDO); “unfortunately” is anagram indicator; to occlude e.g. a passage or cavity is to stop, cover, block it