Margaret with expression of surprise — maiden showing a lot of resistance (6)
I believe the answer is:
megohm
'a lot of resistance' is the definition.
(megohm is a unit of electrical resistance)
'margaret with expression of surprise maiden' is the wordplay.
'margaret' becomes 'meg'.
'with' means one lot of letters go next to another.
'expression of surprise' becomes 'oh'.
'maiden' becomes 'm' (cricket abbreviation).
'meg'+'oh'+'m'='MEGOHM'
'showing' is the link.
(Other definitions for megohm that I've seen before include "a lot of resistance?" , "a good deal of resistance" , "Large unit of resistance" .)