Context : The existence of lithium-rich low-mass red giant stars still represents a challenge for stellar evolution models .
Stellar clusters are privileged environments for this kind of investigation .

Aims : To investigate the chemical abundance pattern of the old open cluster Trumpler 5 , we observed a sample of four red-clump stars with high-resolution optical spectrographs .
One of them ( # 3416 ) reveals extremely strong lithium lines in its spectrum .

Methods : One-dimensional , local thermodynamic equilibrium analysis was performed on the spectra of the observed stars .
A 3D-NLTE analysis was performed to derive the lithium abundance of star # 3416 .

Results : Star # 3416 is super Li-rich with A ( Li ) =3.75 dex .
The lack of ^ { 6 } Li enrichment ( ^ { 6 } Li/ ^ { 7 } Li < 2 % ) , the low carbon isotopic ratio ( ^ { 12 } C/ ^ { 13 } C=14 \pm 3 ) , and the lack of evidence for radial velocity variation or enhanced rotational velocity ( v \sin i = 2.8 \mathrm { km~ { } s } ^ { -1 } ) all suggest that lithium production has occurred in this star through the Cameron & Fowler mechanism .

Conclusions : We identified a super Li-rich core helium-burning , red-clump star in an open cluster .
Internal production is the most likely cause of the observed enrichment .
Given the expected short duration of a star ’ s Li-rich phase , enrichment is likely to have occurred at the red clump or in the immediately preceding phases , namely during the He-flash at the tip of the red giant branch ( RGB ) or while ascending the brightest portion of the RGB .