Some claim a gin expands figure (7)
I believe the answer is:
Here is my best explanation:
'figure' is the definition.
'some claim a gin expands' is the subsidiary indication.
'some' indicates a hidden word (some of the parts of the word are used).
'imagine' is hidden in the letters of 'claim a gin expands'.
(Other definitions for imagine that I've seen before include "Number one", "Picture mentally", "Enigma, I? (anag)", "that Lennon composed", "Fancy - Lennon song", "Form a mental picture", "Suspect", "Dream up", "Conceive; fancy" and "Form a mental image in the mind".)