Notice breakdown in communication, perhaps, at sea (6)
I believe the answer is:
adrift
'at sea' is the definition.
(drifting at sea)
'notice breakdown in communication' is the wordplay.
'notice' becomes 'ad' (both can mean an advertisement).
'breakdown in communication' becomes 'rift' (a rift is an estrangement or disagreement).
'ad'+'rift'='ADRIFT'
'perhaps' is the link.
(Other definitions for adrift that I've seen before include "Moving aimlessly, unfastened" , "out of touch" , "Floating freely, not moored" , "Rudderless, astray" , "'Floating without direction, not tied up (6)'" .)