### Clue: Scientist loves squeezing large marrow (7)
### Answer: OLOGIST 
 ### Explanation: Definition: Scientist 
 [ O,O(2 x letter signifying 0,"love" in tennis scores) **containing**(squeezing) L(abbrev. for "large") ] + GIST(the substance;the central idea;the marrow, of, say, a speech).
Defn: An informal term for an expert in a scientific field, from the suffix used in, say, "biologist", "ecologist", etc.