Exercise system I discovered in full-page book illustrations (7)
I believe the answer is:
pilates
'exercise system' is the definition.
(pilates is an exercise method)
'i discovered in full-page book illustrations' is the wordplay.
'i' becomes 'compiler' (the person who set this crossword).
'discovered' means to look at the middle letters (dis-covered - outer letters removed).
'in full-page book illustrations' becomes 'lates' (I can't explain this - if you can you should believe this answer much more).
The central letters of 'compiler' are 'pi'.
'pi'+'lates'='PILATES'
Can you help me to learn more?
(Other definitions for pilates that I've seen before include "regime for improved fitness" , "attributed to Biblical procurator?" , "Pleats I arrange into a form of exercise" , "Modern exercise" , "discipline?" .)