Old female has walked round stern (2-5)
I believe the answer is:
po-faced
'stern' is the definition.
(po-faced means stern or prudish)
'old female has walked round' is the wordplay.
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'female' becomes 'f' (abbreviation).
'has' says to put letters next to each other.
'walked' becomes 'paced' (pacing is a kind of walking).
'round' means one lot of letters goes inside another.
'o'+'f'='of'
'of' put within 'paced' is 'PO-FACED'.
(Other definitions for po-faced that I've seen before include "Informally solemn in appearance, like nocturnal vessel?" , "Glum" , "With a disapproving countenance" , "Humourless and disapproving" , "With disapproving look" .)