Struggling this week.
18a For instance, bone comprises optimum insulating material (8)
Asbestos?
1d. Chicago station record framed by Mark? (5)
Depot? ‘Ep’ for record (does anyone under 60 understand this meaning?) inside ‘dot’ for mark, but why Chicago station?
42d. Labour with dual winch, alternately operated by fluid (9)
Hydraulic? It matches my crossing letters but I can only parse ‘winch alternately’ is ‘ic’.