Tell him to explore research. It will benefit him more than clinical experience because, quite frankly, an undergraduate doesn't generally have the requisite training to provide any sort of mental health intervention service effectively. For instance, the advice quoted below suggests that a BA level person is doing SI/HI assessments on their own and merely consulting afterwards. That is a troubling amount of responsibility given to someone without formal training in clinical symptom assessment. While having 'clinical stories' may be useful, it does not ensure that you are doing effective service or making reasonable calls which supervision would be able to pick apart (thus, APA pushing for observation as part of required training). This is why suicide hotlines are not call-forwarded to a volunteer's home and why they typically require fairly extensive amounts of on site training before allowing people to answer calls. Research will give (a) an increased capacity to complete the dissertation by being knowledgeable about research design and (b) an improved understanding of how to digest scientific literature, which should inform future clinical practice. If they opt to engage in any sort of 'clinical practice', they should be selective and don't make the assumption that 'more responsibility = better'. This is true of any training, but building bad habits early doesn't ensure better habits later.
I say this as an R1 faculty member and as a former clinical supervisor for several QMHPs.