Take too much vermouth during day periodically? This is rum (6)
I believe the answer is:
oddity
'rum' is the definition.
Although both the answer and definition are singular nouns, I cannot see how they can define each other.
'take too much vermouth during day periodically?' is the wordplay.
'take too much' becomes 'OD' (overdose).
'vermouth' becomes 'it' (short for 'Italian vermouth' as in 'gin and it').
'during' indicates putting letters inside.
'periodically?' indicates alternate letters (letters must be selected 'every so often').
The alternate letters of 'day' are 'dy'.
'it' going within 'dy' is 'dity'.
'od'+'dity'='ODDITY'
'this is' is the link.
Can you help me to learn more?
(Other definitions for oddity that I've seen before include "Something peculiar or unusual" , "Curious item" , "Something strange or peculiar" , "Toy did (anag.)" , "Strange person/thing" .)