President beginning to touch bottom (5)
I believe the answer is:
trump
'president' is the definition.
(Donald Trump)
'beginning to touch bottom' is the wordplay.
'beginning to' indicates taking the first letters.
'bottom' becomes 'rump' (rump can informally mean someone's bottom).
The first letter of 'touch' is 't'.
't'+'rump'='TRUMP'
(Other definitions for trump that I've seen before include "Outplay" , "Powerful playing card" , "Card beating other suits" , "Powerful card - the last one to be heard at the Day of Judgement" , "Card of the most powerful suit" .)