Stem from small lecture (5)
I believe the answer is:
stalk
'stem' is the definition.
(I know that stem can be written as stalk)
'small lecture' is the wordplay.
'small' becomes 's' (abbreviation - e.g. clothes size).
'lecture' becomes 'talk' (synonyms).
's'+'talk'='STALK'
'from' is the link.
(Other definitions for stalk that I've seen before include "Quietly pursue" , "Stem; follow" , "Follow sneakily" , "Stem of plant" , "Follow prey stealthily" .)