Derrick's supporter mounting horse, on the go! (6)
I believe the answer is:
gantry
'derrick's supporter' is the definition.
Although both the answer and definition are singular nouns, I don't understand how one could define the other.
'mounting horse on the go' is the wordplay.
'mounting' says the letters should be written backwards (going up in a down clue).
'horse' becomes 'nag' (nag is a kind of horse).
'on' means one lot of letters go next to another.
'the go' becomes 'try' (I've seen this before).
'nag' written backwards gives 'gan'.
'gan'+'try'='GANTRY'
Can you help me to learn more?
(Other definitions for gantry that I've seen before include "Bridging framework to support crane, signals etc" , "Bridge-like framework for moblile crane" , "Kind of bridge for supporting moving crane" , "platform" , "Overhead structure supporting equipment" .)