Feel and be strangely weak (6)
I believe the answer is:
Here is my best explanation:
'weak' is the definition.
('feeble' can be similar in meaning to 'weak')
'feel and be strangely' is the wordplay.
'and' means one lot of letters go next to another.
'strangely' is an anagram indicator.
'feelbe' with letters rearranged gives 'FEEBLE'.
(Other definitions for feeble that I've seen before include "Weak or ineffective", "Wimpish", "lacking resolve", "Physically weak or lacking effectiveness", "Ineffective", "Frail", "rather weak", "Lacking force", "Weak from illness or age" and "Weak - unconvincing".)