Turning around, ruffian grabs publicity thing (6)
I believe the answer is:
Here is my best explanation:
'thing' is the definition.
(I've seen this before)
'turning around ruffian grabs publicity' is the wordplay.
'turning around' is a reversal indicator.
'ruffian' becomes 'hood'.
'grabs' indicates putting letters inside.
'publicity' becomes 'ad' (advert).
'hood' enclosing 'ad' is 'hadood'.
'hadood' back-to-front is 'DOODAH'.
(Other definitions for doodah that I've seen before include "Thingummy", "Thingamy", "one can't name", "Thing whose name you can't remember", "Some object", "Whatsit", "thingummy", "Gizmo, thingamabob", "Ornament" and "Whatchamacallit, thingamajig".)