Completely baffled by 18 down- A disc or cylindrical part that slides to and fro in a hollow cylinder; part of an internal combustion engine.(6) M?ST?N. A|ny help appreciated,thank you.
Aarrgghh! Just reread the across clue,it IS typeface! Can't believe I didn't spot my error.That'll teach me to read the clue properly in future. Anyway,many thanks Jammydodgem,FoxLee,and ddon.