Give someone a sharp reminder? (5)
I believe the answer is:
nudge
'reminder?' is the definition.
(I've seen this before)
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for nudge that I've seen before include "Encouraging prompt" , "Gentle prod" , "A gentle reminder?" , "Remind (with the elbow?)" , "Remind, prompt gently" .)