Retrosynthesis of spirocyclic compounds?
Step 1 - Form the anion of your starting material ($\ce{NaOEt/EtOH}$ will do this nicely) and react with phenethyl bromide ($\ce{PhCH2CH2Br}$).

Step 2 - Add the product to hot polyphosphoric acid$\ce{^{[1]}}$ to cyclize it to the required product.  

Reference


Cyclization of Aryl-Aliphatic Esters with Phosphorus Pentoxide in Phosphoric Acid by Richard C. Gilmore, Journal of the American Chemical Society, 1951, 73 (12), 5879-5880, DOI: 10.1021/ja01156a521