Coffee blend somewhat lacking in strength (6)
I believe the answer is:
feeble
'lacking in strength' is the definition.
(I've seen this before)
'coffee blend somewhat' is the wordplay.
'somewhat' says the answer is hidden in the clue.
'FEEBLE' is hidden within 'coffee blend'.
(Other definitions for feeble that I've seen before include "Weak or ineffective" , "Weak, debilitated" , "Weak, lacking strength" , "Paltry" , "Wimpish" .)