19a Drifters work out what to do with four letters from the 11th (8)
?L?N?T?N
Plankton, as a rather arch definition of drifters?
I can almost but not quite parse this one:
35a Tanker with late British figurehead on front of ship (6)
Bowser, I think. Er = late British figurehead. Front of ship is either bow, then how is the 's' explained, or it is the 's' (front of ship), then how is the bow explained?