Talking point one in best clubs (5)
I believe the answer is:
topic
'talking point' is the definition.
(I've seen this before)
'one in best clubs' is the wordplay.
'one' becomes 'i' (Roman numeral).
'in' means one lot of letters goes inside another.
'best' becomes 'top' (top can mean the very best).
'clubs' becomes 'c' (abbreviation used in card games such as bridge).
'top'+'c'='topc'
'i' placed inside 'topc' is 'TOPIC'.
(Other definitions for topic that I've seen before include "Subject (of, eg, speech)" , "Something to discuss" , "Talking point" , "might this be hot?" , "Subject (of speech, etc)" .)