Fail to remember (6)
![Ross](/clue/static/ross-mug.min.png)
I believe the answer is:
forget
'fail to remember' is the definition.
(synonyms)
This is all the clue.
(Other definitions for forget that I've seen before include "Stop thinking about" , "Be unable to recall" , "Leave behind unintentionally" , "Fail to remember" , "Overlook" .)