Horse and zebras periodically escaping pounds (8)
I believe the answer is:
smackers
'escaping pounds' is the definition.
I can't judge whether this defines the answer.
'horse and zebras periodically' is the wordplay.
'horse' becomes 'smack' (synonyms).
'and' means one lot of letters go next to another.
'periodically' means one should take alternating letters (letters must be selected 'every so often').
The alternate letters of 'zebras' are 'ers'.
'smack'+'ers'='SMACKERS'
Can you help me to learn more?
(Other definitions for smackers that I've seen before include "People striking" , "money" , "worth more than one pound" , "big kisses" , "Parents enforcing discipline perhaps" .)