Threatening good learner in university year (4)
I believe the answer is:
ugly
'threatening' is the definition.
(I've seen this before)
'good learner in university year' is the wordplay.
'good' becomes 'g' (abbreviation).
'learner' becomes 'l'.
'in' means one lot of letters goes inside another.
'university' becomes 'u'.
'year' becomes 'y'.
'g'+'l'='gl'
'u'+'y'='uy'
'gl' inserted inside 'uy' is 'UGLY'.
(Other definitions for ugly that I've seen before include "offensive to look at" , "Difficult to look at" , "Extremely unattractive" , "Menacing" , "Frightful" .)