Shrewd, pinching joker's last crack (6)
I believe the answer is:
cranny
'crack' is the definition.
(I've seen this before)
'shrewd pinching joker's last' is the wordplay.
'shrewd' becomes 'canny' (I've seen this before).
'pinching' means one lot of letters goes inside another (taking inside).
'joker's last' becomes 'r' (I am not sure about this - if you are sure you should believe this answer much more).
'canny' placed around 'r' is 'CRANNY'.
Can you help me to learn more?
(Other definitions for cranny that I've seen before include "Fissure - chink" , "corner" , "confined space" , "Secret place (searched after nook)" , "Small opening or crevice" .)