In a grid, perhaps, a line that doesn't bend (5)
I believe the answer is:
rigid
'in a grid perhaps a line that doesn't bend' is the definition.
Both the answer and definition are adjectives. Maybe there's a link between them I don't understand?
'in a grid perhaps a line' is the wordplay.
'in' indicates putting letters inside.
'perhaps' indicates an anagram.
'a line' becomes 'i' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'grid' anagrammed gives 'rigd'.
'rigd' going around 'i' is 'RIGID'.
Can you help me to learn more?
(Other definitions for rigid that I've seen before include "Uncompromising" , "completely" , "strict" , "not relaxing" , "unwilling to move" .)