Hear working is an attempt to deceive (3-2)
I believe the answer is:
try-on
'is an attempt to deceive' is the definition.
(I've seen this before)
'hear working' is the subsidiary indication.
'hear' becomes 'try' ('try' can be a synonym of 'hear').
'working' becomes 'on'.
'try'+'on'='tryon'
(Other definitions for try-on that I've seen before include "An attempt to deceive" , "Test a garment" , "Attempt to fool someone" , "Don garment to see if it fits" , "Test (clothes) for size" .)