Leader in Texas behind president (5)
I believe the answer is:
trump
'president' is the definition.
(Donald Trump)
'leader in texas behind' is the wordplay.
'leader in' suggests taking the first letters.
'behind' becomes 'rump' (informal term for the buttocks).
The initial letter of 'texas' is 't'.
't'+'rump'='TRUMP'
(Other definitions for trump that I've seen before include "High card" , "Playing card with designated added value" , "US President" , "Brick" , "Powerful card - the last one to be heard at the Day of Judgement" .)