A German with silver ra-ra skirts overturned jelly (4-4)
I believe the answer is:
agar agar
'jelly' is the definition.
(I've seen this before)
'a german with silver ra-ra skirts overturned' is the wordplay.
'german' becomes 'g' (abbreviation).
'with' means one lot of letters go next to another.
'silver' becomes 'Ag' (Ag is the chemical symbol for silver).
'skirts' is an insertion indicator (skirt can mean to go around).
'overturned' says the letters should be written in reverse.
'ra'+'ra'='rara'
'ag' going into 'rara' is 'ragara'.
'ragara' written backwards gives 'aragar'.
'a'+'g'+'aragar'='AGAR-AGAR'
(Other definitions for agar agar that I've seen before include "seaweed" , "It contributes to culture" , "jelly" , "gelatinous substance" , "Growth medium used in lab" .)