Almost consider being slim! (4)
I believe the answer is:
thin
'being slim' is the definition.
('thin' can be similar in meaning to 'slim')
'almost consider' is the wordplay.
'almost' means to remove the last letter (most of the word but not all of it).
'consider' becomes 'think' (I've seen this before).
'think' with its final letter removed is 'THIN'.
(Other definitions for thin that I've seen before include "Superficial" , "Implausible" , "as 7 [LOAF] may be sliced" , "Unconvincing" , "Scrawny" .)