Tag lines written about Lincoln, say (5)
I believe the answer is:
label
'tag' is the definition.
(I know that tag can be written as label)
'lines written about lincoln say' is the wordplay.
'lines' becomes 'l' (abbreviation as in lines of poetry).
'written about lincoln say' becomes 'abel' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'l'+'abel'='LABEL'
Can you help me to learn more?
(Other definitions for label that I've seen before include "Mark" , "Descriptive tag" , "Means of identifying" , "Tag, tab" , "Identification tag" .)