Clue: Having eaten joints, Mum needs a gym to get trim (9)
Answer: SHIPSHAPE
Explanation: Having eaten joints, Mum needs a gym to get trim (9)
SH ("mum", as in "keep mum") + **A** + **P.E.** ("gym"), *having eaten* **HIPS** ("joints"), so **S(HIPS)H-A-P.E.