Indeed was at length held up (7)
I believe the answer is:
delayed
'held up' is the definition.
(similar in meaning)
'indeed was at length' is the wordplay.
I cannot quite understand how this works, but
'indeed' could be 'aye' (I've seen this before) and 'aye' is located in the answer.
'length' could be 'l' (abbreviation in geometry) and 'l' is found within the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for delayed that I've seen before include "Held up, back" , "Shelved" , "Deferred, postponed" , "Made late" , "Put back" .)