Manifest lie about Northern Rock! (8)
I believe the answer is:
tangible
'manifest' is the definition.
(thesaurus)
'lie about northern rock' is the wordplay.
'lie' becomes 'tale' (I've seen this before).
'about' is an insertion indicator.
'northern' becomes 'n' (abbreviation e.g. N. Ireland).
'rock' becomes 'gib' (both are nicknames for Gibraltar).
'n'+'gib'='ngib'
'tale' going around 'ngib' is 'TANGIBLE'.
(Other definitions for tangible that I've seen before include "asset" , "Real, solid" , "Able to be perceived by touch" , "Solid, can be touched" , "Palpable" .)