She's at least pushing fifty in it! (6)
I believe the answer is:
stella
'she's' is the definition.
(I've seen this before)
'at least pushing fifty in it' is the wordplay.
'at' means one lot of letters go next to another.
'least pushing' becomes 'tel' (I can't explain this - if you can you should believe this answer much more).
'fifty' becomes 'L' (Roman numeral).
'in' means one lot of letters goes inside another.
'it' becomes 'sa' (old-fashioned abbreviation for sex appeal).
'tel' put next to 'l' is 'tell'.
'tell' inserted inside 'sa' is 'STELLA'.
Can you help me to learn more?
(Other definitions for stella that I've seen before include "woman" , "Paul McCartney's daughter" , "lady?" , "- Gibbons (Cold Comfort Farm)" , "Swift alias for Esther" .)