Student in Lincoln qualified (4)
I believe the answer is:
able
'qualified' is the definition.
(thesaurus)
'student in lincoln' is the wordplay.
'student' becomes 'l' (as in L-plates for learner drivers**).
'in' is an insertion indicator.
'lincoln' becomes 'abe'.
'l' going into 'abe' is 'ABLE'.
(Other definitions for able that I've seen before include "Bright" , "- -bodied; - seaman" , "accomplished" , "Competent as, say, sailor" , "Skilled" .)