Unopened lager? That's weird (5)
I believe the answer is:
eerie
'weird' is the definition.
(both can mean strange or unsettling)
'unopened lager? that's' is the wordplay.
'unopened' means to remove the first letter (without opening letter).
'lager?' becomes 'beer' (lager is a kind of beer).
'that's' becomes 'ie'.
'beer' with its initial letter taken away is 'eer'.
'eer'+'ie'='EERIE'
(Other definitions for eerie that I've seen before include "Weird and disturbing" , "Oddly frightening" , "Spooky, unearthly" , "Awesome" , "Strange, unusual" .)