Second secretary with oil magnate picked up dish (9)
I believe the answer is:
spaghetti
'dish' is the definition.
'second secretary with oil magnate picked up' is the wordplay.
'second' becomes 's' (common abbreviation).
'secretary' becomes 'pa' (abbreviation for personal assistant).
'with' means one lot of letters go next to another.
'oil magnate' becomes 'Getty' (J Paul Getty, founder of the Getty Oil Company).
'picked up' indicates a 'sounds like' (homophone) clue.
'getty' is a homophone of 'ghetti'.
's'+'pa'+'ghetti'='SPAGHETTI'
(Other definitions for spaghetti that I've seen before include "Solid strings of pasta" , "2 [PASTA]" , "Italian serving" , "It's past eight, time for strange pasta" , "Strings of pastas" .)