Skilled student in Lincoln (4)
I believe the answer is:
able
'skilled' 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' inserted within 'abe' is 'ABLE'.
(Other definitions for able that I've seen before include "Clever skilful" , "Competent as seaman may be" , "Competent - sort of seaman" , "Showing skill" , "Practised" .)