Second opening for lecturer? I’m not promising (4)
I believe the answer is:
slim
'not promising' is the definition.
(as in slim chances)
'second opening for lecturer? i'm' is the wordplay.
'second' becomes 's' (common abbreviation).
'opening for' indicates taking the first letters.
'i'm' becomes 'im' ().
The initial letter of 'lecturer' is 'l'.
's'+'l'+'im'='SLIM'
(Other definitions for slim that I've seen before include "Bakery produce" , "Slender and elegant" , "insufficient" , "Thin (person); small (chance)" , "Annual horse race" .)