Look and act like a senior straddling horse (6)
I believe the answer is:
behold
'look' is the definition.
(thesaurus)
'act like a senior straddling horse' is the wordplay.
I cannot really see how this works, but
'act' could be 'hold' (hold is a kind of act) and 'hold' is found within the answer.
The remaining letters 'be' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...
'and' acts as a link.
Can you help me to learn more?
(Other definitions for behold that I've seen before include "Lo - look!" , "Lo, see here" , "Look to the poet" , "Archaic injunction to look" , "Look upon" .)