Be straight and count on rising position (4,2,3)

'be straight' is the definition.
I don't know anything about this answer so I cannot tell whether this works.

'count on rising position' is the wordplay.
'count' becomes 'tell' (I've seen this before).
'rising' says the letters should be written in reverse (in a down clue, letters go up).
'position' becomes 'lie' (lie can mean to place or position).
'on' reversed gives 'no'.
'tell'+'no'+'lie'='TELL NO LIE'

'and' is the link.

Can you help me to learn more?