Search all over, securing lecturer (5)
I believe the answer is:
rifle
'search' is the definition.
(as in rifling around for something)
'all over securing lecturer' is the wordplay.
'all over' becomes 'rife' (I've seen this in another clue).
'securing' indicates putting letters inside.
'lecturer' becomes 'l' (abbreviation for lecturer).
'rife' enclosing 'l' is 'RIFLE'.
(Other definitions for rifle that I've seen before include "Flier (anag.)" , "disarray" , "Steal and carry off - firearm" , "lock, stock and barrel" , "Long-barrelled weapon, normal army equipment" .)