Different signs I had put inside the shunting areas (7)
I believe the answer is:
sidings
'inside the shunting areas' is the definition.
I can't tell whether this definition defines the answer.
'different signs i had' is the wordplay.
'different' is an anagram indicator (letters placed in a different order).
'had' becomes 'd' (I've seen this in other clues).
'signs'+'i'+'d'='signsid'
'signsid' is an anagram of 'SIDINGS'.
'put' is the link.
Can you help me to learn more?
(Another definition for sidings that I've seen is " railway stores".)