Measured drinks in the army mess presumably (5)
I believe the answer is:
units
'army mess presumably' is the definition.
I can't tell whether this definition defines the answer.
'measured drinks in the' is the wordplay.
'measured' becomes 'unis' (I can't justify this - if you can you should believe this answer much more).
'drinks in' indicates putting letters inside (inserted letters are drank in).
'the' becomes 't' (the is pronounced as a 't' sound in some dialects).
'unis' placed around 't' is 'UNITS'.
Can you help me to learn more?
(Other definitions for units that I've seen before include "Modules" , "Measures of alcohol" , "Figure on the right" , "Apparatus similar to barbecue" , "Detachments" .)