A MOP is a tool used for cleaning floors, usually consisting of an absorbent material attached to a long handle. It is often used to soak up liquid spills and to scrub dirt off of hard surfaces. The term 'messy hairdo' is often used to describe a hairstyle that is unkempt and disheveled. The crossword solution for this term is MOP, which is a fitting answer as it can be used to describe the action of trying to tame a wild and unruly hairstyle.