A reminder that George is inside, naked (5)
I believe the answer is:
nudge
'a reminder' is the definition.
(I've seen this before)
'george is inside naked' is the wordplay.
'george' becomes 'g'.
'is inside' is an insertion indicator.
'naked' becomes 'nude' ('nude' can be a synonym of 'naked'**).
'g' placed within 'nude' is 'NUDGE'.
'that' is the link.
(Other definitions for nudge that I've seen before include "Encouraging prompt" , "Gently encourage" , "Gentle poke with elbow" , "Gentle push" , "Light touch or push" .)