Almost fail to get strong fish out of water (6)
I believe the answer is:
misfit
'fish out of water' is the definition.
(I've seen this before)
'almost fail to get strong' is the wordplay.
'almost' means to remove the last letter (most of the word but not all of it).
'fail to get' becomes 'miss' (I've seen this before).
'strong' becomes 'fit' (I've seen this before).
'miss' with its final letter taken off is 'mis'.
'mis'+'fit'='MISFIT'
(Other definitions for misfit that I've seen before include "An oddity, doesn't integrate with others" , "Fish out of water" , "One who is out of place" , "Oddball" , "Person unsuited to environment" .)