Period added to the end of a sentence (4,4)
I believe the answer is:
full stop
'period' is the definition.
(I know that period can be written as full stop)
'added to the end of a sentence' is the wordplay.
I cannot quite see how this works, but
'to' is found in the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for full stop that I've seen before include "period in America" , "Punctuation mark - period" , "finalised" , "Point" , "Period of sentence" .)