Most creepy wild steer that is entered (7)
I believe the answer is:
eeriest
'most creepy' is the definition.
(I've seen this in another clue)
'wild steer that is entered' is the wordplay.
'wild' is an anagram indicator.
'that is' becomes 'ie' (short for Latin 'id est', 'that is').
'entered' is an insertion indicator.
'steer' is an anagram of 'eerst'.
'eerst' enclosing 'ie' is 'EERIEST'.
(Other definitions for eeriest that I've seen before include "Strangest" , "beating stranger" , "Most ghostly" , "Most weird" , "Most strange and frightening" .)