Oddball sailor working over marines by a lake (8)

I believe the answer is:

abnormal

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'oddball' is the definition.
(thesaurus)

'sailor working over marines by a lake' is the wordplay.
'sailor' becomes 'ab' (abbreviation for able seaman).
'working over marines' becomes 'norma' (I can't justify this - if you can you should believe this answer much more).
'by' is a charade indicator (letters next to each other).
'a lake' becomes 'l' (geographical abbreviation).
'ab'+'norma'+'l'='ABNORMAL'

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(Other definitions for abnormal that I've seen before include "like 15 [ANOMALIES]" , "Deviating from the standard" , "Deviant, different from the usual" , "Rum" , "Unusual, atypical" .)

I've seen this clue in The Guardian.

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