Perhaps fillies west of Tennessee oddly lacking judgment (5,5)
I believe the answer is:
horse sense
'judgment' is the definition.
(horse sense is a kind of judgment)
'perhaps fillies west of tennessee oddly lacking' is the wordplay.
'perhaps fillies' becomes 'horses'.
'west of' says to put letters next to each other.
'oddly lacking' means one should take alternating letters.
The alternate letters of 'tennessee' are 'ense'.
'horses'+'ense'='HORSE SENSE'
(Other definitions for horse sense that I've seen before include "Practical wisdom" , "Gumption" , "good thinking" , "Good reasoning" , "Practical judgment" .)