Clue: Compiler returned and hooked up with someone doing the Eden Project? (5)
Answer: EMMET
Explanation: Definition: someone doing the Eden Project
**<=ME** ("compiler") *returned and* **MET** ("hooked up with") 
"Emmet" is a Cornish word for a non-Cornish, especially toursists, who when in Cornwall may well be "doing" (ie visiting) the Eden Project.