Essential to secure company for rambling (10)
I believe the answer is:
incoherent
'for rambling' is the definition.
(similar in meaning)
'essential to secure company' is the wordplay.
'essential' becomes 'inherent' (I've seen this in another clue).
'to secure' is an insertion indicator (inserted letters are secured inside).
'company' becomes 'co' (abbreviation).
'inherent' going around 'co' is 'INCOHERENT'.
(Other definitions for incoherent that I've seen before include "Confused" , "drunk?" , "difficult to understand" , "rambling" , "Internally inconsistent" .)