Step up seeing jockey having a change of heart (5)
I believe the answer is:
riser
'step up' is the definition.
(rising part of a stair)
'jockey having a change of heart' is the wordplay.
'jockey' becomes 'ris' (I can't explain this - if you can you should believe this answer much more).
'having' says to put letters next to each other.
'a change' becomes 'conversion' (conversion is a kind of change).
'of heart' says to take the centre (I've seen 'heart' mean this).
The central letters of 'conversion' are 'er'.
'ris'+'er'='RISER'
'seeing' acts as a link.
Can you help me to learn more?
(Other definitions for riser that I've seen before include "Upright piece in stairs" , "person advancing position?" , "Front of a staircase step" , "I get up" , "Vertical upward pipe" .)