16A Devices for copying or enlarging maps (9)
_I_G_A_H_ Assumedly -I-graphs, but the only word I can find which meets the definition is pantograph - no fit!
42A Intercalary month of the Jewish calendar added in a Leap year (4, 6)
Clearly ADAR then - I-h-n
52A Entrance passageways to subterranean tombs (6)
_R_M_E