Perform at the gala opening, if you follow (3)
I believe the answer is:
dog
'you follow' is the definition.
'dog' can be an answer for 'follow' (dog can mean to follow or torment). I'm not sure about the 'you' bit.
'perform at the gala opening' is the wordplay.
'perform' becomes 'do' (both can mean complete an action).
'at' means one lot of letters go next to another.
'opening' suggests taking the first letters.
The initial letter of 'gala' is 'g'.
'do'+'g'='DOG'
'if' is the link.
Can you help me to learn more?
(Other definitions for dog that I've seen before include "Lassie" , "Worry" , "Domesticated canine" , "A pet; its life prov. wretched" , "Domestic animal" .)