Deduce subordinate has abandoned one old Romeo (5)
I believe the answer is:
infer
'deduce' is the definition.
(I know that deduce can be written as infer)
'subordinate has abandoned one old romeo' is the wordplay.
'subordinate has' becomes 'in' (I can't justify this - if you can you should believe this answer much more).
'abandoned' says to hollow out the word (remove centre letters) (middle letters abandon or vacate the word).
'one old' becomes 'foregone' (foregone can mean past).
'romeo' becomes 'r' (phonetic alphabet: alpha, bravo, charlie etc.).
'foregone' with its middle taken out is 'fe'.
'in'+'fe'+'r'='INFER'
Can you help me to learn more?
(Other definitions for infer that I've seen before include "Extrapolate, conclude" , "Derive as a consequence" , "Deduce, surmise" , "Draw a conclusion" , "Conclude or judge from facts" .)