Need university dons to write lines (6)
I believe the answer is:
penury
'need' is the definition.
(I know that need can be written as penury)
'university dons to write lines' is the wordplay.
'university' becomes 'u' (abbreviation for university).
'dons' means one lot of letters goes inside another (don means to wear or put on).
'to write' becomes 'pen' (synonyms).
'lines' becomes 'ry' (abbreviation for railway).
'pen'+'ry'='penry'
'u' put within 'penry' is 'PENURY'.
(Other definitions for penury that I've seen before include "privation" , "Extreme destitution" , "Real poverty" , "Indigence, destitution" , "Destitution, need" .)