Arrogant, having an IQ of 150? (3,6,2,4)
I believe the answer is:
too clever by half
'arrogant' is the definition.
'an iq of 150?' is the wordplay.
I cannot quite see how this works, but
'an' could be 'a' and 'a' is found in the answer.
'of' could be 'o' and 'o' is found in the answer.
'150?' could be 'cl' and 'cl' is present in the answer.
This explanation may well be incorrect...
'having' acts as a link.
(Other definitions for too clever by half that I've seen before include "Play" , "shrewd, but flawed by excessive complexity" .)