Polly, to Tom (4)
I believe the answer is:
aunt
'polly to tom' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for aunt that I've seen before include "Parent's female sibling" , "Female relation" , "Charley's ___ , farce staged in London in 1892, revived and adapted ever since" , "Uncle's wife" , "Charley's in play?" .)