Ran back into line that was cramped (6)
I believe the answer is:
narrow
'cramped' is the definition.
(I've seen this before)
'ran back into line' is the wordplay.
I cannot really understand how this works, but
an anagram of 'ran' is 'nar' which is within the answer.
'line' could be 'row' (a row or line of things) and 'row' is found within the answer.
No letters remain.
This explanation may well be incorrect...
'that was' is the link.
Can you help me to learn more?
(Other definitions for narrow that I've seen before include "Lacking tolerance" , "with little to spare" , "limit" , "Vessel designed for canals" , "contract" .)