Old druid drained rum (3)
I believe the answer is:
odd
'rum' is the definition.
(rum can mean strange or dubious)
'old druid drained' is the wordplay.
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'drained' suggests removing the centre.
'druid' with its middle taken out is 'dd'.
'o'+'dd'='ODD'
(Other definitions for odd that I've seen before include "Peculiar sort of number?" , "Bizarre - occasional" , "Peculiar in uneven way" , "Not even? That's peculiar" , "Not even - curious" .)