Poor feeder, pike's first observed in very British river (4,7)
I believe the answer is:
soup kitchen
'poor feeder' is the definition.
(I've seen this before)
'pike's first observed in very british river' is the wordplay.
I cannot really see how this works, but
'first' could be 'i' (I in Roman numerals eg Elizabeth I) and 'i' is located in the answer.
'very' could be 'so' (both can mean 'extremely') and 'so' is present in the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for soup kitchen that I've seen before include "mobile food stall" , "Centre for feeding those in need" , "Eating-place" , "Poor feeder" , "Where volunteers supply food to the homeless" .)