Have a quick look around Tower (4)
I believe the answer is:
keep
'tower' is the definition.
(thesaurus)
'have a quick look around' is the wordplay.
'have a quick look' becomes 'peek'.
'around' says the letters should be written in reverse.
'peek' reversed gives 'KEEP'.
(Other definitions for keep that I've seen before include "Guard" , "Hold - part of castle" , "Central tower of castle" , "Act as custodian of" , "Retain or care for" .)