Commercial break no longer fixed in position (6)
I believe the answer is:
adrift
'no longer fixed in position' is the definition.
(I've seen this before)
'commercial break' is the wordplay.
'commercial' becomes 'ad' (abbreviation for advertisement).
'break' becomes 'rift' (rift can mean a break or opening).
'ad'+'rift'='ADRIFT'
(Other definitions for adrift that I've seen before include "out of touch" , "No longer fixed in position" , "like Mary Celeste?" , "Disoriented" , "(Of ship) out of control" .)