Text Mark about visiting Tom? (5)
I believe the answer is:
caret
'text mark' is the definition.
'caret' can be an answer for 'mark' (caret is a kind of mark). I'm not sure about the 'text' bit.
'about visiting tom?' is the wordplay.
'about' becomes 're' ('re' means regarding or about).
'visiting' means one lot of letters goes inside another.
'tom?' becomes 'cat' (a tom is a male cat).
're' going inside 'cat' is 'CARET'.
Can you help me to learn more?
(Other definitions for caret that I've seen before include "Proofreading sign for 'Insert'" , "this reveals something missing" , "Indicator of omission" , "Proofreader's sign of omission" , "It shows what to put in" .)