Helen's mum picked up on road north to Delaware's state capital (8)
I believe the answer is:
adelaide
'state capital' is the definition.
(state capital of South Australia)
'helen's mum picked up on road north to delaware's' is the wordplay.
'helen's mum' becomes 'leda' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'picked up' shows that the letters should be reversed in order.
'on' says to put letters next to each other.
'road north' becomes 'AI' (resembling Al, road from London to Edinburgh).
'to delaware' becomes 'DE' (standard two letter abbrev).
'leda' in reverse letter order is 'adel'.
'adel'+'ai'+'de'='ADELAIDE'
Can you help me to learn more?
(Other definitions for adelaide that I've seen before include "Antipodean city" , "South Australia's capital" , "cook turkey on the barbie here?" , "Woman" , "Lead aide to Oz" .)