About to visit a girl grown up by this time (7)
I believe the answer is:
already
'by this time' is the definition.
(I've seen this before)
'about to visit a girl grown up' is the wordplay.
'about' becomes 're' (regarding).
'to visit' means one lot of letters goes inside another (inserted letters visit others).
'girl grown up' becomes 'lady'.
'a'+'lady'='alady'
're' inserted within 'alady' is 'ALREADY'.
(Other definitions for already that I've seen before include "As early as this, so soon?" , "Indication of impatience (US)" , "thus far" , "Previously" , "By the time in question" .)