Understand trick (4,2)
I believe the answer is:
take in
I believe this is a double definition.
'understand' is the first definition.
(I've seen this before)
'trick' is the second definition.
(thesaurus)
(Other definitions for take in that I've seen before include "Shelter - hoodwink" , "Enclose; deceive" , "Fraud" , "Cheat" , "Provide with shelter, or delude" .)