Perfectly rig a ruler for cheating (9)
I believe the answer is:
irregular
'cheating' is the definition.
Both the definition and answer are adjectives. Perhaps they are linked in a way I don't understand?
'perfectly rig a ruler' is the wordplay.
'rig a ruler' can be anagrammed to 'IRREGULAR'.
However, I'm not clear how the anagram is indicated.
'for' is the link.
Can you help me to learn more?
(Other definitions for irregular that I've seen before include "Out of the ordinary" , "Uneven - inappropriate" , "somewhat odd" , "Rough - dishonest" , "Unpredictable" .)