Horseman heard to choose an entrance (7)
I believe the answer is:
picador
'horseman' is the definition.
(I've seen this before)
'heard to choose an entrance' is the wordplay.
'heard' indicates a 'sounds like' (homophone) clue.
'to choose' becomes 'pick' (picking is a kind of choosing).
'an entrance' becomes 'ador' (I can't justify this - if you can you should give a lot more credence to this answer).
'pick' sounds like 'pic'.
'pic'+'ador'='PICADOR'
Can you help me to learn more?
(Other definitions for picador that I've seen before include "ringfighter" , "Cop raid to get bullfighter on horseback" , "Animal killer" , "Mounted bullfighter with a lance" , "The bullfighter who goads the animal" .)