Taking advantage of the situation, capital invested in rubbishing of poor MP (11)
I believe the answer is:
opportunism
'taking advantage of the situation' is the definition.
'capital invested in rubbishing of poor mp' is the wordplay.
'capital' becomes 'tunis' (Tunis is an example).
'invested in' means one lot of letters goes inside another.
'rubbishing of' is an anagram indicator (I've seen 'rubbish' mean this (a poor quality or rubbish spelling of the letters)).
'poor'+'mp'='poormp'
'poormp' with letters rearranged gives 'opporm'.
'tunis' inserted within 'opporm' is 'OPPORTUNISM'.
(Other definitions for opportunism that I've seen before include "Making the most of favourable moments" , "Expediency" .)