Rough idea about a dismissed cable (7)
I believe the answer is:
outline
'rough idea' is the definition.
(I've seen this before)
'a dismissed cable' is the wordplay.
'a dismissed' becomes 'out' (dismissed in cricket).
'cable' becomes 'line' (synonyms).
'out'+'line'='OUTLINE'
'about' is the link.
(Other definitions for outline that I've seen before include "Sketch, skeleton" , "Possibly tracing" , "(Make a) sketch" , "(Give) schematic account" , "Sketch or contour" .)