He's one I singled out to behave stubbornly (3,2,4,5)
I believe the answer is:
dig in ones heels
'behave stubbornly' is the definition.
(I've seen this before)
'he's one i singled out' is the wordplay.
'out' is an anagram indicator (out can mean wrong or inaccurate).
'hes'+'one'+'i'+'singled'='hesoneisingled'
'hesoneisingled' is an anagram of 'DIG IN ONES HEELS'.
'to' is the link.
(Other definitions for dig in ones heels that I've seen before include "make an impression at grass-roots level?" , "Be very stubborn" .)