Modify and enrich obstacle (9)
I believe the answer is:
hindrance
'obstacle' is the definition.
(a hindrance is an obstacle or barrier)
'modify and enrich' is the wordplay.
'modify' indicates an anagram (I've seen this in other clues).
'and'+'enrich'='andenrich'
'andenrich' with letters rearranged gives 'HINDRANCE'.
(Other definitions for hindrance that I've seen before include "Impediment" , "Obstruction" , "barrier" , "Delay to overcome" , "bar" .)