Nothing on old, empty beer bottles was unusual (5,3)
I believe the answer is:
stood out
'unusual' is the definition.
The answer and definition are different parts of speech. However, past participle verbs and adjectives can sometimes define each other.
'nothing on old empty beer bottles' is the wordplay.
'nothing on' becomes 'o' (I've seen this in other clues).
'empty' suggests removing the centre.
'beer' becomes 'stout' (type of beer).
'bottles' is an insertion indicator (to bottle can mean to contain).
'old' with its middle removed is 'od'.
'o'+'od'='ood'
'ood' put within 'stout' is 'STOOD OUT'.
'was' is the link.
Can you help me to learn more?
(Other definitions for stood out that I've seen before include "Was conspicuous" , "very noticeable" , "Was proud" , "Offered resistance - didn''t go unnoticed" .)