Cockney's to give assistance carrying last serving of gefilte fish (7)

I haven't cracked this one yet — but the brilliant team at Fifteensquared have:

<gefilt> E (“last serving of” means last letter only) in <h> ELP OUT (=to give assistance; “Cockney’s” means letter “h” is dropped); according to Chambers , an eelpout is the burbot or viviparous blenny