Tipsy barman keeping old line in rum (8)
I believe the answer is:
abnormal
'rum' is the definition.
(I've seen this before)
'tipsy barman keeping old line' is the wordplay.
'tipsy' indicates an anagram.
'keeping' is an insertion indicator.
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'line' becomes 'l' (used when specifying particular lines from a poem).
'barman' anagrammed gives 'abnrma'.
'abnrma' placed around 'o' is 'abnorma'.
'abnorma'+'l'='ABNORMAL'
'in' acts as a link.
(Other definitions for abnormal that I've seen before include "Deviant, different from the usual" , "Different from what is usual or accepted" , "Deviant or unnatural" , "Highly unusual" , "Anomalous" .)